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  • 1. Aaboud, B
    et al.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    Sidebo, P. Edvin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    Search for scalar leptoquarks in pp collisions at √s = 13 TeV with the ATLAS experiment2016Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 18, nr 9, artikkel-id 093016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a search for first generation scalar leptoquarks using 1.03 fb(-1) of proton-proton collisions data produced by the Large Hadron Collider at root s = 7 TeV and recorded by the ATLAS experiment. Leptoquarks are sought via their decay into an electron or neutrino and a quark, producing events with two oppositely charged electrons and at least two jets, or events with an electron, missing transverse momentum and at least two jets. Control data samples are used to validate background predictions from Monte Carlo simulation. In the signal region, the observed event yields are consistent with the background expectations. We exclude at 95% confidence level the production of first generation scalar leptoquark with masses m(LQ) < 660 (607) GeV when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).

  • 2. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    A search for new physics in dijet mass and angular distributions in pp collisions at root s=7 TeV measured with the ATLAS detector2011Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, s. 053044-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for new interactions and resonances produced in LHC proton-proton (pp) collisions at a centre-of-mass energy root s = 7 TeV was performed with the ATLAS detector. Using a dataset with an integrated luminosity of 36 pb(-1), dijet mass and angular distributions were measured up to dijet masses of similar to 3.5 TeV and were found to be in good agreement with Standard Model predictions. This analysis sets limits at 95% CL on various models for new physics: an excited quark is excluded for mass between 0.60 and 2.64 TeV, an axigluon hypothesis is excluded for axigluon masses between 0.60 and 2.10 TeV and quantum black holes are excluded in models with six extra space-time dimensions for quantum gravity scales between 0.75 and 3.67 TeV. Production cross section limits as a function of dijet mass are set using a simplified Gaussian signal model to facilitate comparisons with other hypotheses. Analysis of the dijet angular distribution using a novel technique simultaneously employing the dijet mass excludes quark contact interactions with a compositeness scale 3 below 9.5 TeV.

  • 3. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC2011Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, s. 053033-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Measurements are presented from proton-proton collisions at centre-of-mass energies of root s = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo (MC) models, including a new AMBT1 pythia6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the MC models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks with p(T) > 100 MeV, is measured to be 3.483 +/- 0.009 (stat) +/- 0.106 (syst) at root s = 0.9 TeV and 5.630 +/- 0.003 (stat) +/- 0.169 (syst) at root s = 7 TeV.

  • 4. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at root s=7TeV with the ATLAS detector2014Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, s. 113013-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to allhadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of root s = 7 TeV and correspond to an integrated luminosity of 4.6 fb(-1). The measurement is performed by reconstructing the boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet centre-ofmass frame is used to suppress the large multi-jet background. The cross-section for events with a hadronically decaying W or Z boson, with transverse momentum p(T) > 320 GeV and pseudorapidity |eta| < 1.9, is measured to be sigma W+ Z= 8.5 +/- 1.7 pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques.This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to allhadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of root s = 7 TeV and correspond to an integrated luminosity of 4.6 fb(-1). The measurement is performed by reconstructing the boosted W or Z bosons in single jets. The reconstructed jet mass is used to identify the W and Z bosons, and a jet substructure method based on energy cluster information in the jet centre-ofmass frame is used to suppress the large multi-jet background. The cross-section for events with a hadronically decaying W or Z boson, with transverse momentum p(T) > 320 GeV and pseudorapidity |eta| < 1.9, is measured to be sigma W+ Z= 8.5 +/- 1.7 pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques.

  • 5. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Morley, Anthony
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for excited electrons and muons in root s=8 TeV proton-proton collisions with the ATLAS detector2013Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 15, s. 093011-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ATLAS detector at the Large Hadron Collider is used to search for excited electrons and excited muons in the channel pp -> ll* -> ll gamma, assuming that excited leptons are produced via contact interactions. The analysis is based on 13 fb(-1) of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excited-lepton mass m(l*). For m(l*) >= 0.8 TeV, the respective upper limits on sigma B(l(*) -> l gamma) are 0.75 and 0.90 fb for the e* and mu* searches. Limits on sigma B are converted into lower bounds on the compositeness scale 3. In the special case where Lambda = m(l*), excited-electron and excited-muon masses below 2.2 TeV are excluded.

  • 6. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    Search for extra dimensions in diphoton events from proton-proton collisions at root s=7 TeV in the ATLAS detector at the LHC2013Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 15, s. 043007-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton-proton collisions at root s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9 fb(-1). The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani-Hamed, Dimopoulos and Dvali, 95% confidence level lower limits of between 2.52 and 3.92 TeV are set on the ultraviolet cutoff scale MS depending on the number of extra dimensions and the theoretical formalism used. In the context of the Randall-Sundrum model, a lower limit of 2.06 (1.00) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of k/(M) over bar (Pl) = 0.1(0.01). Combining with the ATLAS dilepton searches based on the 2011 data, the 95% confidence level lower limit on the Randall-Sundrum graviton mass is further tightened to 2.23 (1.03) TeV for k/(M) over bar (Pl) = 0.1(0.01).

  • 7. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Measurement of hard double-parton interactions in W(-> lv) plus 2-jet events at root s=7 TeV with the ATLAS detector2013Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 15, s. 033038-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The production of W bosons in association with two jets in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36 pb(-1), collected with the ATLAS detector at the Large Hadron Collider. The fraction of events arising from double-parton interactions, f(DP)((D)), has been measured through the p(T) balance between the two jets and amounts to f(DP)((D)) = 0.08 +/- 0.01 (stat.) +/- 0.02 (sys.) for jets with transverse momentum p(T) > 20 GeV and rapidity vertical bar y vertical bar < 2.8. This corresponds to a measurement of the effective area parameter for hard double-parton interactions of sigma(eff) = 15 +/- 3 (stat.)(-3)(+5) (sys.) mb.

  • 8. Aad, G.
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for WH production with a light Higgs boson decaying to prompt electron-jets in proton-proton collisions at root s=7 TeV with the ATLAS detector2013Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 15, s. 043009-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search is performed for WH production with a light Higgs boson decaying to hidden-sector particles resulting in clusters of collimated electrons, known as electron-jets. The search is performed with 2.04 fb(-1) of data collected in 2011 with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at root s = 7 TeV. One event satisfying the signal selection criteria is observed, which is consistent with the expected background rate. Limits on the product of the WH production cross section and the branching ratio of a Higgs boson decaying to prompt electron-jets are calculated as a function of a Higgs boson mass in the range from 100 to 140 GeV.

  • 9. Aad, G.
    et al.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Sidebo, P. Edvin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    A search for an excited muon decaying to a muon and two jets in pp collisions at root s=8 TeV with the ATLAS detector2016Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 18, artikkel-id 073021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Anew search signature for excited leptons is explored. Excited muons are sought in the channel pp -> mu mu* -> mu mu jet jet, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb(-1) of pp collision data at a centre-of-mass energy of root s = 8 TeV taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass m(mu)*. For m(mu)* between 1.3 and 3.0 TeV, the upper limit on sigma B(mu* -> mu q (q) over bar) is between 0.6 and 1 fb. Limits on sB are converted to lower bounds on the compositeness scale Lambda. In the limiting case Lambda = m(mu)*, excited muons with a mass below 2.8 TeV are excluded. With the same model assumptions, these limits at larger mu* masses improve upon previous limits from traditional searches based on the gauge-mediated decay mu* -> mu gamma.

  • 10.
    Abergel, David
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Edge, Jonathan M.
    Balatsky, Alexander V.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    The role of spin-orbit coupling in topologically protected interface states in Dirac materials2014Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, s. 065012-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We highlight the fact that two-dimensional (2D) materials with Dirac-like low energy band structures and spin-orbit coupling (SOC) will produce linearly dispersing topologically protected Jackiw-Rebbi modes at interfaces where the Dirac mass changes sign. These modes may support persistent spin or valley currents parallel to the interface, and the exact arrangement of such topologically protected currents depends crucially on the details of the SOC in the material. As examples, we discuss buckled 2D hexagonal lattices such as silicene or germanene, and transition metal dichalcogenides such as MoS2.

  • 11.
    Andersson, Mauritz
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Berglind, Eilert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Björk, Gunnar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Orbital angular momentum modes do not increase the channel capacity in communication links2015Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 17, artikkel-id 043040Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The orbital momentum of optical or radio waves can be used as a degree of freedom to transmit information. However, mainly for technical reasons, this degree of freedom has not been widely used in communication channels. The question is if this degree of freedom opens up a new, hitherto unused 'communication window' supporting 'an infinite number of channels in a given, fixed bandwidth' in free space communication as has been claimed? We answer this question in the negative by showing that on the fundamental level, the mode density, and thus room for mode multiplexing, is the same for this degree of freedom as for sets of modes lacking angular momentum. In addition we show that modes with angular momentum are unsuitable for broadcasting applications due to excessive crosstalk or a poor signal-to-noise ratio.

  • 12. Annibaldi, S. V.
    et al.
    Ivlev, A. V.
    Konopka, U.
    Ratynskaia, Svetlana V.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Thomas, H. M.
    Morfill, G. E.
    Lipaev, A. M.
    Molotkov, V. I.
    Petrov, O. F.
    Fortov, V. E.
    Dust-acoustic dispersion relation in three-dimensional complex plasmas under microgravity2007Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of dedicated experiments with the Plasma Kristal Experiment ( PKE)-Nefedov ( Nefedov et al 2003 New J. Phys. 5 33) set-up were performed on board the International Space Station to measure the dispersion relation ( DR) for the longitudinal dust-acoustic ( DA) waves in quasi-isotropic three-dimensional ( 3D) complex plasmas. The waves were excited by applying ac electric modulation of variable frequency to the radio frequency ( rf) electrodes. The amplitude of excitation was varied with frequency to ensure a 'sufficiently linear' regime of the dust density perturbations. The DR was obtained by measuring the induced density perturbations, revealing fairly good agreement with a simple multispecies theory of DA waves.

  • 13.
    Aurell, Erik
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Beräkningsbiologi, CB. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Aalto Univ, Finland.
    Eichhorn, Ralf
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Sweden.
    On the von Neumann entropy of a bath linearly coupled to a driven quantum system2015Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 17, artikkel-id 065007Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The change of the von Neumann entropy of a set of harmonic oscillators initially in thermal equilibrium and interacting linearly with an externally driven quantum system is computed by adapting the Feynman-Vernon influence functional formalism. This quantum entropy production has the form of the expectation value of three functionals of the forward and backward paths describing the system history in the Feynman-Vernon theory. In the classical limit of Kramers-Langevin dynamics (Caldeira-Leggett model) these functionals combine to three terms, where the first is the entropy production functional of stochastic thermodynamics, the classical work done by the system on the environment in units of k(B)T, and the second and the third other functionals which have no analogue in stochastic thermodynamics.

  • 14.
    Belonoshko, Anatoly B.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Kondenserade materiens teori.
    Derlet, P. M.
    Mikhaylushkin, A. S.
    Simak, S. I.
    Hellman, O.
    Burakovsky, L.
    Swift, D. C.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Quenching of bcc-Fe from high to room temperature at high-pressure conditions: a molecular dynamics simulation2009Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The new high-temperature (T), high-pressure (P), body-centered cubic (bcc) phase of iron has probably already been synthesized in recent diamond anvil cell (DAC) experiments (Mikhaylushkin et al 2007 Phys. Rev. Lett. 99 165505). These DAC experiments on iron revealed that the high-PT phase on quenching transforms into a mixture of close-packed phases. Our molecular dynamics simulation and structural analysis allow us to provide a probable interpretation of the experiments. We show that quenching of the high-PT bcc phase simulated with the embedded-atom model also leads to the formation of the mixture of close-packed phases. Therefore, the assumption of the stability of the high-PT bcc iron phase is consistent with experimental observation.

  • 15.
    Björk, Gunnar
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Shabbir, Saroosh
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Non-monotonic projection probabilities as a function of distinguishability2014Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, s. 013006-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Typically, quantum superpositions, and thus measurement projections of quantum states involving interference, decrease (or increase) monotonically as a function of increased distinguishability. Distinguishability, in turn, can be a consequence of decoherence, for example caused by the (simultaneous) loss of excitation or due to inadequate mode matching (either deliberate or indeliberate). It is known that for some cases of multi-photon interference a non-monotonic decay of projection probabilities occurs, which has so far been attributed to interference between four or more photons. We show that such a non-monotonic behavior of projection probabilities is not unnatural, and can also occur for single-photon and even semiclassical states. Thus, while the effect traces its roots from indistinguishability and thus interference, the states for which this can be observed do not need to have particular quantum features.

  • 16.
    Björk, Gunnar
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Shabbir, Saroosh
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Reply to comment on ‘non-monotonic projection probabilities as a function of distinguishability’2014Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, nr 11, artikkel-id 118004Artikkel i tidsskrift (Fagfellevurdert)
  • 17.
    Blom, Martin
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Minakata, H
    Unity of CP and T violation in neutrino oscillations2004Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 6, s. 130-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a previous work, a simultaneous P-CP[P] and P-T [P] biprobability plot was proposed as a useful tool for a unified graphical description of CP and T violation in neutrino oscillations. The diamond-shaped structure of the plot is understood as a consequence of the approximate CP-CP and T-CP relations obeyed by the oscillation probabilities. In this paper, we take a step forward towards a deeper understanding of the unified graphical representation by showing that these two relations are identical in their content, suggesting a truly unifying view of CP and T violation in neutrino oscillations. We suspect that the unity reflects the underlying CPT theorem. We also present a calculation of corrections to the CP-CP and the T-CP relations to leading order in Deltam(21)(2)/Deltam(31)(2) and s(13)(2).

  • 18. Boezio, M.
    et al.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Picozza, P.
    Sparvoli, R.
    Spillantini, P.
    Adriani, O.
    Barbarino, G. C.
    Bazilevskaya, G. A.
    Bellotti, R.
    Bogomolov, E. A.
    Bonechi, L.
    Bongi, M.
    Bonvicini, V.
    Borisov, S.
    Bottai, S.
    Bruno, A.
    Cafagna, F.
    Campana, D.
    Carbone, R.
    Carlson, Per
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Casolino, M.
    Castellini, G.
    Consiglio, L.
    De Pascale, M. P.
    De Santis, C.
    De Simone, N.
    Di Felice, V.
    Galper, A. M.
    Grishantseva, L.
    Gillard, William
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Hofverberg, Petter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Koldashov, S. V.
    Krutkov, S. Y.
    Kvashnin, A. N.
    Leonov, A.
    Malvezzi, V.
    Marcelli, L.
    Menn, W.
    Mikhailov, V. V.
    Mocchiutti, E.
    Mori, N.
    Nikonov, N.
    Osteria, G.
    Papini, P.
    Ricci, M.
    Ricciarini, S. B.
    Simon, M.
    Stozhkov, Y. I.
    Vacchi, A.
    Vannuccini, E.
    Vasilyev, G.
    Voronov, S. A.
    Yurkin, Y. T.
    Zampa, G.
    Zampa, N.
    Zverev, V. G.
    PAMELA and indirect dark matter searches2009Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11, s. 105023-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a review of the experimental results obtained by PAMELA in measuring the (p, (p) over bar ) and e(+/-) abundance in cosmic rays. In this context, we discuss the interpretation of the observed anomalous positron excess in terms of the annihilation of dark matter particles as well as in terms of standard astrophysical sources. Moreover we show the constraints on dark matter models from (p) over bar data.

  • 19.
    Brandenburg, Axel
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Rogachevskii, Igor
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Kleeorin, Nathan I.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Magnetic concentrations in stratified turbulence: The negative effective magnetic pressure instability2016Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 18, nr 12, artikkel-id 125011Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the presence of strong density stratification, hydromagnetic turbulence attains qualitatively new properties: the formation of magnetic flux concentrations. We review here the theoretical foundations of this mechanism in terms of what is now called the negative effective magnetic pressure instability. We also present direct numerical simulations of forced turbulence in strongly stratified layers and discuss the qualitative and quantitative similarities with corresponding mean-field simulations. Finally, the relevance to sunspot formation is discussed.

  • 20. Buzzicotti, Michele
    et al.
    Bhatnagar, Akshay
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Biferale, Luca
    Lanotte, Alessandra S.
    Ray, Samriddhi Sankar
    Lagrangian statistics for Navier-Stokes turbulence under Fourier-mode reduction: fractal and homogeneous decimations2016Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 18, artikkel-id 113047Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study small-scale and high-frequency turbulent fluctuations in three-dimensional flows under Fourier-mode reduction. The Navier-Stokes equations are evolved on a restricted set of modes, obtained as a projection on a fractal or homogeneous Fourier set. We find a strong sensitivity (reduction) of the high-frequency variability of the Lagrangian velocity fluctuations on the degree of mode decimation, similarly to what is already reported for Eulerian statistics. This is quantified by a tendency towards a quasi-Gaussian statistics, i.e., to a reduction of intermittency, at all scales and frequencies. This can be attributed to a strong depletion of vortex filaments and of the vortex stretching mechanism. Nevertheless, we found that Eulerian and Lagrangian ensembles are still connected by a dimensional bridge-relation which is independent of the degree of Fourier-mode decimation.

  • 21. Chang, J.
    et al.
    Sassa, Y.
    Guerrero, S.
    Mansson, M.
    Shi, M.
    Pailhes, S.
    Bendounan, A.
    Mottl, R.
    Claesson, T.
    Tjernberg, Oscar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Patthey, L.
    Ido, M.
    Oda, M.
    Momono, N.
    Mudry, C.
    Mesot, J.
    Electronic structure near the 1/8-anomaly in La-based cuprates2008Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report an angle-resolved photoemission study of the electronic structure of the pseudogap state in La1.48Nd0.4Sr0.12CuO4 (T-c < 7 K). Two opposite dispersing Fermi arcs are the main result of this study. Several scenarios that can explain this observation are discussed.

  • 22. Diaz, R. G.
    et al.
    Romero, J. L.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Bourennane, M.
    Certainty relations between local and nonlocal observables2005Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We point out that for an arbitrary number of identical particles, each defined on a Hilbert space of arbitrary dimension, there exists a whole ladder of relations of complementarity between certain local and nonlocal measurements corresponding to every conceivable grouping of the particles, e. g., the more accurately we can know ( by a measurement) some joint property of three qubits ( projecting the state onto a tripartite-entangled state), the less accurate some other property, local to the three qubits, becomes. We investigate the relation between these complementarity relations and a similar relation based on interference visibilities. We also show that the complementarity relations are particularly tight for particles defined on prime dimensional Hilbert spaces.

  • 23.
    Ergül, Adem
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Lidmar, Jack
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Statistisk fysik.
    Johansson, Jan
    Azizoglu, Yagiz
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Schaeffer, David
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Haviland, David B.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Localizing quantum phase slips in one-dimensional Josephson junction chains2013Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 15, s. 095014-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We studied quantum phase-slip (QPS) phenomena in long one-dimensional Josephson junction series arrays with tunable Josephson coupling. These chains were fabricated with as many as 2888 junctions, where one sample had a separately tunable link in the middle of the chain. Measurements were made of the zero-bias resistance, R-0, as well as current-voltage characteristics (IVC). The finite R-0 is explained by QPS and shows an exponential dependence on root E-J/E-C with a distinct change in the exponent at R-0 = R-Q = h/4e(2). When R-0 > R-Q, the IVC clearly shows a remnant of the Coulomb blockade, which evolves to a zero-current state with a sharp critical voltage as E-J is tuned to a smaller value. The zero-current state below the critical voltage is due to coherent QPSs and we show that these are enhanced when the central link is weaker than all other links. Above the critical voltage, a negative, differential resistance is observed, which nearly restores the zero-current state.

  • 24.
    Eskandari, Hossein
    et al.
    Ferdowsi Univ Mashhad, Dept Elect Engn, Mashhad, Razavi Khorasan, Iran..
    Majedi, Mohammad Saeed
    Ferdowsi Univ Mashhad, Dept Elect Engn, Mashhad, Razavi Khorasan, Iran..
    Attari, Amir Reza
    Ferdowsi Univ Mashhad, Dept Elect Engn, Mashhad, Razavi Khorasan, Iran..
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknisk teori och konstruktion.
    Elliptical generalized Maxwell fish-eye lens using conformal mapping2019Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 21, artikkel-id 063010Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A circular graded index lens is conformally transformed to an elliptical shape using a closed-form transformation. The proposed transformation is then employed to compress a Maxwell fish-eye and its generalized version. Since the transformation is conformal, the electromagnetic properties of the device are perfectly preserved after the transformation with fully isotropic and dielectric-only materials. Ray-tracing and full-wave simulations are carried out for several cases to verify the functionality of the optically transformed lenses in geometrical optics and wave optics regimes.

  • 25.
    Fransson, Jonas
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Non-equilibrium triplet blockade in parallel coupled quantum dots2006Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 8, s. 114-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is theoretically demonstrated that parallel weakly tunnel coupled quantum dots exhibit non-equilibrium blockade regimes caused by a full occupation in the spin triplet state, in analogy to the Pauli spin blockade in serially weakly coupled quantum dots. Charge tends to accumulate in the two-electron triplet for bias voltages that support transitions between the singlet and three-electron states.

  • 26. Galteland, Peder Notto
    et al.
    Babaev, Egor
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
    Sudbo, Asle
    Thermal remixing of phase-separated states in two-component bosonic condensates2015Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 17, artikkel-id 103040Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider a two-component interacting bosonic condensate with dominating intra-species repulsive density-density interactions. We study the phase diagram of the system at finite temperature with rotation, using large-scale Monte Carlo simulations of a two-component Ginzburg-Landau model of the system. In the presence of rotation, the system features a competition between long-range vortex-vortex interactions and short-range density-density interactions. This leads to a rotation-driven 'mixing' phase transition in a spatially inhomogeneous state with a broken U(1) symmetry. Thermal fluctuations in this state lead to nematic two-component sheets of vortex liquids. At sufficiently strong inter-component interaction, we find that the superfluid and Z(2) phase transitions split. This results in the formation of an intermediate state which breaks only Z(2) symmetry. It represents two phase separated normal fluids with a difference in their densities.

  • 27. Hakkarainen, T.
    et al.
    Setala, T.
    Friberg, Ari T.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Near-field imaging of interacting nano objects with metal and metamaterial superlenses2012Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, s. 043019-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Employing rigorous electromagnetic theory we investigate optical the near-field imaging of two interacting dipole-like objects with metal and slightly lossy metamaterial nanoslab superlenses. Our analysis indicates that the dipole emission is suppressed by near-field interactions when the objects are close to the lens or each other. This strongly influences the image quality, in particular with objects of small size and high polarizability. The interference from two nearby objects also affects the resolution and subwavelength definition can only be obtained for objects with dipole moments predominantly orthogonal to the slab. Such an optimal imaging condition is achieved with excitation by total internal reflection. With simulations we show that in these circumstances, subwavelength resolutions of about lambda/5 for silver superlens and lambda/10 for metamaterial slab are reached.

  • 28.
    He, Sailing
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Jin, Y.
    Ruan, Z. C.
    Kuang, J. G.
    On subwavelength and open resonators involving metamaterials of negative refraction index2005Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 7Artikkel i tidsskrift (Fagfellevurdert)
  • 29. Horowitz, Jordan M.
    et al.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Second-law-like inequalities with information and their interpretations2014Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, s. 125007-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a thermodynamic process with measurement and feedback, the second law of thermodynamics is no longer valid. In its place, various second-law-like inequalities have been advanced that each incorporate a distinct additional term accounting for the information gathered through measurement. We quantitatively compare a number of these information measures using an analytically tractable model for the feedback cooling of a Brownian particle. We find that the information measures form a hierarchy that reveals a web of interconnections. To untangle their relationships, we address the origins of the information, arguing that each information measure represents the minimum thermodynamic cost to acquire that information through a separate, distinct measurement procedure.

  • 30.
    Javanmard, Younes
    et al.
    Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany..
    Trapin, Daniele
    Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany..
    Bera, Soumya
    Indian Inst Technol, Dept Phys, Bombay 400076, Maharashtra, India..
    Bardarson, Jens H.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kondenserade materiens teori.
    Heyl, Markus
    Max Planck Inst Phys Komplexer Syst, D-01187 Dresden, Germany..
    Sharp entanglement thresholds in the logarithmic negativity of disjoint blocks in the transverse-field Ising chain2018Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 20, artikkel-id 083032Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Entanglement has developed into an essential concept for the characterization of phases and phase transitions in ground states of quantum many-body systems. In this work we use the logarithmic negativity to study the spatial entanglement structure in the transverse-field Ising chain both in the ground state and at nonzero temperatures. Specifically, we investigate the entanglement between two disjoint blocks as a function of their separation, which can be viewed as the entanglement analog of a spatial correlation function. We find sharp entanglement thresholds at a critical distance beyond which the logarithmic negativity vanishes exactly and thus the two blocks become unentangled, which holds even in the presence of long-ranged quantum correlations, i.e., at the system's quantum critical point. Using time-evolving block decimation, we explore this feature as a function of temperature and size of the two blocks and present a simple model to describe our numerical observations.

  • 31. Kadigrobov, A. M.
    et al.
    Shekhter, R. I.
    Kulinich, S. I.
    Jonson, M.
    Balkashin, O. P.
    Fisun, V. V.
    Naidyuk, Yu G.
    Yanson, I. K.
    Andersson, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Korenivski, Vladislav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Hot electrons in magnetic point contacts as a photon source2011Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, s. 023007-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose to use a point contact between a ferromagnetic and a normal metal in the presence of a magnetic field for creating a large inverted spin population of hot electrons in the contact core. The key point of the proposal is that when these hot electrons relax by flipping their spin, microwave photons are emitted, with a frequency tunable by the applied magnetic field. While point contacts are an established technology, their use as a photon source is a new and potentially very useful application. We show that this photon emission process can be detected by means of transport spectroscopy and demonstrate stimulated emission of radiation in the 10-100 GHz range for a model point contact system using a minority-spin ferromagnetic injector. These results can potentially lead to new types of lasers based on spin injection in metals.

  • 32. Kibis, O. , V
    et al.
    Kyriienko, Oleksandr
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Shelykh, I. A.
    Structure of surface electronic states in strained mercury telluride2019Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 21, artikkel-id 043016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the theory describing the various surface electronic states arisen from the mixing of conduction and valence bands in a strained mercury telluride (HgTe) bulk material. We demonstrate that the strain-induced band gap in the Brillouin zone center of HgTe results in the surface states of two different kinds. Surface states of the first kind exist in the small region of electron wave vectors near the center of the Brillouin zone and have the Dirac linear electron dispersion characteristic for topological states. The surface states of the second kind exist only far from the center of the Brillouin zone and have the parabolic dispersion for large wave vectors. The structure of these surface electronic states is studied both analytically and numerically in the broad range of their parameters, aiming to develop its systematic understanding for the relevant model Hamiltonian. The results bring attention to the rich surface physics relevant for topological systems.

  • 33.
    Kothe, Christian
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Kvantelektronik och -optik, QEO.
    Björk, Gunnar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Kvantelektronik och -optik, QEO.
    Inoue, Shuichiro
    Bourennane, Mohamed
    On the efficiency of quantum lithography2011Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, s. 043028-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum lithography promises, in principle, unlimited feature resolution, independent of wavelength. However, in the literature, at least two different theoretical descriptions of quantum lithography exist. They differ in the extent to which they predict that the photons retain spatial correlation from generation to absorption, and although both predict the same feature size, they vastly differ in predicting how efficiently a quantum lithographic pattern can be exposed. Until recently, essentially all quantum lithography experiments have been performed in such a way that it is difficult to distinguish between the two theoretical explanations. However, last year an experiment was performed that gives different outcomes for the two theories. We comment on the experiment and show that the model that fits the data unfortunately indicates that the trade-off between resolution and efficiency in quantum lithography is very unfavourable.

  • 34. Lagoudakis, Konstantinos G.
    et al.
    McMahon, Peter L.
    Fischer, Kevin A.
    Puri, Shruti
    Mueller, Kai
    Dalacu, Dan
    Poole, Philip J.
    Reimer, Michael E.
    Zwiller, Val
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvantelektronik och -optik, QEO.
    Yamamoto, Yoshihisa
    Vuckovic, Jelena
    Initialization of a spin qubit in a site-controlled nanowire quantum dot2016Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 18, artikkel-id 053024Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fault-tolerant quantum repeater or quantum computer using solid-state spin-based quantum bits will likely require a physical implementation with many spins arranged in a grid. Self-assembled quantum dots (QDs) have been established as attractive candidates for building spin-based quantum information processing devices, but such QDs are randomly positioned, which makes them unsuitable for constructing large-scale processors. Recent efforts have shown that QDs embedded in nanowires can be deterministically positioned in regular arrays, can store single charges, and have excellent optical properties, but so far there have been no demonstrations of spin qubit operations using nanowire QDs. Here we demonstrate optical pumping of individual spins trapped in site-controlled nanowire QDs, resulting in high-fidelity spin-qubit initialization. This represents the next step towards establishing spins in nanowire QDs as quantum memories suitable for use in a large-scale, fault-tolerant quantum computer or repeater based on all-optical control of the spin qubits.

  • 35. Laguardia, L.
    et al.
    Cremona, A.
    De Angeli, M.
    Lazzaro, E.
    Ratynskaia, Svetlana
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Passoni, M.
    Dellasega, D.
    Gervasini, G.
    Grosso, G.
    Schiavone, R.
    Vassallo, E.
    Formation of dust in low-pressure magnetized hydrocarbon plasmas2011Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, s. 063006-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The rapid formation of large molecules and the subsequent production of solid-state dust particles in a low-pressure discharge is unlikely, because of the low rates of the polymerization reactions and short lifetimes of the species. Here, we suggest that C dust particles can form in atypically low (10(-3) mbar)-pressure hydrocarbon plasmas if the dust charging time is much shorter than the gas residence time in the device; we present supporting experimental evidence for this. Such a condition can be obtained by the production of high-density plasmas. The results show that dust formation from the gaseous phase can occur in a much wider parameter range than is commonly assumed.

  • 36. Lindblad, Andreas
    et al.
    Kimberg, V
    Söderström, Johan
    Nicolas, C
    Travnikova, O
    Kosugi, N
    Gel’mukhanov, Faris
    Miron, C
    Vibrational scattering anisotropy in O2 -- €”dynamics beyond the Born–Oppenheimer approximation2012Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, nr 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Born–Oppenheimer and Franck–Condon approximations are two major concepts in the interpretation of electronic excitations and modeling of spectroscopic data in the gas and condensed phases. We report large variations of the anisotropy parameter (β) for the fully resolved vibrational sub-states of the X2Πg electronic ground state of O+2 populated by participator resonant Auger decay following excitations of K-shell electrons into the σ☆ resonance by monochromatic x-rays. Decay spectra for light polarization directions parallel and perpendicular to the electron detection axis recorded at four different excitation energies in the vicinity of the O 1s → σ☆ transition are presented. Breakdown of the Born–Oppenheimer approximation is for the first time selectively observed for the lower vibrational sub-states, where two quantum paths—resonant and direct—leading to the same final cationic state exist. The higher vibrational sub-states can only be populated by resonant photoemission; hence no interference between these channels can occur.

  • 37.
    Marino, E. C.
    et al.
    Univ Fed Rio de Janeiro, Inst Fis, BR-21941972 Rio De Janeiro, RJ, Brazil..
    Niemeyer, D.
    Univ Fed Rio de Janeiro, Inst Fis, BR-21941972 Rio De Janeiro, RJ, Brazil.;Univ Veiga Almeida, BR-20271020 Rio De Janeiro, RJ, Brazil..
    Alves, Van Sergio
    Univ Fed Para, Fac Fis, BR-66075110 Belem, PA, Brazil..
    Hansson, Tony Hans
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Dept Phys, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden.
    Moroz, Sergej
    Tech Univ Munich, Dept Phys, D-85748 Garching, Germany..
    Screening and topological order in thin superconducting films2018Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 20, artikkel-id 083049Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We derive an effective two-dimensional low-energy theory for thin superconducting films coupled to a three-dimensional fluctuating electromagnetic field. Using this theory we discuss plasma oscillations, interactions between charges and vortices and extract the energy of a vortex. Having found that the effective theory properly describes the long-distance physics, we then use it to investigate to what extent the superconducting film is a topologically ordered phase of matter.

  • 38. Naidyuk, Yu G.
    et al.
    Balkashin, O. P.
    Fisun, V. V.
    Yanson, I. K.
    Kadigrobov, A.
    Shekhter, R. I.
    Jonson, M.
    Neu, V.
    Seifert, M.
    Andersson, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Korenivski, Vladislav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Stimulated emission and absorption of photons in magnetic point contacts2012Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, s. 093021-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Point contacts between high anisotropy ferromagnetic SmCo5 and normal metal Cu are used to achieve a strong spin-population inversion in the contact core. Subjected to microwave irradiation in resonance with the Zeeman splitting in Cu, the inverted spin population relaxes through stimulated spin-flip photon emission, detected as peaks in the point-contact resistance. Resonant spin-flip photon absorption is detected as resistance minima, corresponding to sourcing the photon field energy into the electrical circuit. These results demonstrate fundamental mechanisms that are potentially useful in designing metallic spin-based lasers.

  • 39. Neff, Curtis W.
    et al.
    Andersson, L. Mauritz
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Qiu, Min
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Modelling electromagnetically induced transparency media using the finite-difference time-domain method2007Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Time-domain electromagnetic modelling of complex structures which include both non-dispersive media and media exhibiting electromagnetically induced transparency (EIT) require a general, robust calculation method such as finite-difference time-domain (FDTD). We propose a complex-valued, exact two-pole representation of the permittivity of a three-level system which is suitable for integration into the FDTD algorithm via the auxiliary differential equation method. Our calculation model confirmed reported results which were calculated with an approximate representation of the EIT permittivity. Additionally, propagation calculations which mimic slow light experiments were performed. A major advantage of our representation is the ease with which changes in the control field Rabi frequency can be implemented by using a time-dependent permittivity.

  • 40.
    Nilsson, Daniel
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Uhlén, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Reinspach, Julia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Sinn, H.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Thermal stability of tungsten zone plates for focusing hard x-ray free-electron laser radiation2012Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, s. 043010-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Diffractive Fresnel zone plates made of tungsten show great promise for focusing hard x-ray free-electron laser (XFEL) radiation to very small spot sizes. However, they have to withstand the high-intensity pulses of the beam without being damaged. This might be problematic since each XFEL pulse will create a significant temperature increase in the zone plate nanostructures and it is therefore crucial that the optics are thermally stable, even for a large number of pulses. Here we have studied the thermal stability of tungsten zone-platelike nanostructures on diamond substrates using a pulsed Nd:YAG laser which creates temperature profiles similar to those expected from XFEL pulses. We found that the structures remained intact up to a laser fluence of 100 mJ cm(-2), corresponding to a 6 keV x-ray fluence of 590 mJ cm-2, which is above typical fluence levels in an unfocused XFEL beam. We have also performed an initial damage experiment at the LCLS hard XFEL facility at SLAC National Accelerator Laboratory, where a tungsten zone plate on a diamond substrate was exposed to 105 pulses of 6 keV x-rays with a pulse fluence of 350 mJ cm-2 without any damage occurring.

  • 41.
    Palm, Robin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Korenivski, Vladislav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    A ferrofluid-based neural network: design of an analogue associative memory2009Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyse an associative memory based on a ferrofluid, consisting of a system of magnetic nano-particles suspended in a carrier fluid of variable viscosity subject to patterns of magnetic fields from an array of input and output magnetic pads. The association relies on forming patterns in the ferrofluid during a training phase, in which the magnetic dipoles are free to move and rotate to minimize the total energy of the system. Once equilibrated in energy for a given input-output magnetic field pattern pair, the particles are fully or partially immobilized by cooling the carrier liquid. Thus produced particle distributions control the memory states, which are read out magnetically using spin-valve sensors incorporated into the output pads. The actual memory consists of spin distributions that are dynamic in nature, realized only in response to the input patterns that the system has been trained for. Two training algorithms for storing multiple patterns are investigated. Using Monte Carlo simulations of the physical system, we demonstrate that the device is capable of storing and recalling two sets of images, each with an accuracy approaching 100%.

  • 42. Panda, S. K.
    et al.
    Thunstrom, P.
    Di Marco, I.
    Schott, J.
    Delin, Anna
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Dasgupta, I.
    Eriksson, O.
    Sarma, D. D.
    A charge self-consistent LDA plus DMFT study of the spectral properties of hexagonal NiS2014Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 16, s. 093049-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic structure and spectral properties of hexagonal NiS have been studied in the high temperature paramagnetic phase and low temperature anti-ferromagnetic phase. The calculations have been performed using charge self-consistent density-functional theory in local density approximation combined with dynamical mean-field theory (LDA+DMFT). The photoemission spectra (PES) and optical properties have been computed and compared with the experimental data. Our results show that the dynamical correlation effects are important to understand the spectral and optical properties of NiS. These effects have been analyzed in detail by means of the computed real and imaginary part of the self-energy.

  • 43. Peil, O. E.
    et al.
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Detailed ab initio calculations of the structure and magnetic state of a metallic spin glass2008Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present for the first time a long-sought atomic and magnetic structure of one of the most well-known and studied spin-glass systems: the Cu83Mn17 alloy, which is the prototype for a large class of metallic spin-glass systems. The structure has been determined from simulations based on atomic and magnetic interactions obtained from first-principles calculations. Being in perfect agreement with recent neutron scattering experiments, our results reveal the atomic and magnetic structure that exhibits a specific short-range order (SRO) and is believed to be responsible for a complicated magnetic cluster dynamics leading to the spin-glass behaviour in this alloy. The ordered phase underlying the atomic SRO is shown to have a Cu3Mn-type structure with 16 atoms per unit cell. The magnetic SRO is associated with incommensurate spin-spiral correlations.

  • 44.
    Pinheiro, Fernanda
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Stockholm University, Sweden.
    Matrikainen, J. -P
    Larson, J.
    Phases of d-orbital bosons in optical lattices2015Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 17, artikkel-id 053004Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We explore the properties of bosonic atoms loaded into the d bands of an isotropic square optical lattice. Following the recent experimental success reported in Zhai et al (2013 Phys. Rev. A 87 063638), in which populating d bands with a 99 fidelity was demonstrated, we present a theoretical study of the possible phases that can appear in this system. Using the Gutzwiller ansatz for the three d band orbitals we map the boundaries of the Mott insulating phases. For not too large occupation, two of the orbitals are predominantly occupied, while the third, of a slightly higher energy, remains almost unpopulated. In this regime, in the superfluid phase we find the formation of a vortex lattice, where the vortices come in vortex/anti-vortex pairs with two pairs locked to every site. Due to the orientation of the vortices time-reversal symmetry is spontaneously broken. This state also breaks a discrete -symmetry. We further derive an effective spin-1/2 model that describe the relevant physics of the lowest Mott-phase with unit filling. We argue that the corresponding two dimensional phase diagram should be rich with several different phases. We also explain how to generate anti-symmetric spin interactions that can give rise to novel effects like spin canting.

  • 45. Pollet, L.
    et al.
    Kiselev, M. N.
    Prokof'Ev, Nikolay V
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik.
    Svistunov, B. V.
    Grassmannization of classical models2016Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 18, nr 11, artikkel-id 113025Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Applying Feynman diagrammatics to non-fermionic strongly correlated models with local constraints might seem generically impossible for two separate reasons: (i) the necessity to have a Gaussian (non-interacting) limit on top of which the perturbative diagrammatic expansion is generated by Wick's theorem, and (ii) Dyson's collapse argument implying that the expansion in powers of coupling constant is divergent. We show that for arbitrary classical lattice models both problems can be solved/circumvented by reformulating the high-temperature expansion (more generally, any discrete representation of the model) in terms of Grassmann integrals. Discrete variables residing on either links, plaquettes, or sites of the lattice are associated with the Grassmann variables in such a way that the partition function (as well as all correlation functions) of the original system and its Grassmann-field counterpart are identical. The expansion of the latter around its Gaussian point generates Feynman diagrams. Our work paves the way for studying lattice gauge theories by treating bosonic and fermionic degrees of freedom on equal footing. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

  • 46. Razzoli, E.
    et al.
    Sassa, Y.
    Drachuck, G.
    Mansson, M.
    Keren, A.
    Shay, M.
    Berntsen, Magnus H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Tjernberg, Oscar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Radovic, M.
    Chang, J.
    Pailhes, S.
    Momono, N.
    Oda, M.
    Ido, M.
    Lipscombe, O. J.
    Hayden, S. M.
    Patthey, L.
    Mesot, J.
    Shi, M.
    The Fermi surface and band folding in La2-xSrxCuO4, probed by angle-resolved photoemission2010Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 12, s. 125003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A systematic angle-resolved photoemission study of the electronic structure of La2-xSrxCuO4 in a wide doping range is presented in this paper. In addition to the main energy band, we observed a weaker additional band, the (pi, pi) folded band, which shows unusual doping dependence. The appearance of the folded band suggests that a Fermi surface reconstruction is doping dependent and could already occur at zero magnetic field.

  • 47.
    Reuss, Matthias
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Förds, F.
    Blom, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellulär biofysik. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Öktem, Ozan
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Matematik (Avd.).
    Högberg, B.
    Brismar, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellulär biofysik. KTH, Centra, Science for Life Laboratory, SciLifeLab. Karolinska Institutet, Sweden.
    Measuring true localization accuracy in super resolution microscopy with DNA-origami nanostructures2017Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 19, nr 2, artikkel-id 025013Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A common method to assess the performance of (super resolution) microscopes is to use the localization precision of emitters as an estimate for the achieved resolution. Naturally, this is widely used in super resolution methods based on single molecule stochastic switching. This concept suffers from the fact that it is hard to calibrate measures against a real sample (a phantom), because true absolute positions of emitters are almost always unknown. For this reason, resolution estimates are potentially biased in an image since one is blind to true position accuracy, i.e. deviation in position measurement from true positions. We have solved this issue by imaging nanorods fabricated with DNA-origami. The nanorods used are designed to have emitters attached at each end in a well-defined and highly conserved distance. These structures are widely used to gauge localization precision. Here, we additionally determined the true achievable localization accuracy and compared this figure of merit to localization precision values for two common super resolution microscope methods STED and STORM.

  • 48.
    Russom, Aman
    et al.
    BioMEMS Resource Center, Center for Engineering in Medicine and Surgical Services, Massachusetts General Hospital.
    Gupta, Amit K.
    Nagrath, Sunitha
    Di Carlo, Dino
    Edd, Jon F.
    Toner, Mehmet
    Differential inertial focusing of particles in curved low-aspect-ratio microchannels2009Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 11, s. 075025-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microfluidic-based manipulation of particles is of great interest due to the insight it provides into the physics of hydrodynamic forces. Here, we study a particle-size-dependent phenomenon based on differential inertial focusing that utilizes the flow characteristics of curved, low aspect ratio (channel width >> height), microfluidic channels. We report the emergence of two focusing points along the height of the channel (z-plane), where different sized particles are focused and ordered in evenly spaced trains at correspondingly different lateral positions within the channel cross-section. We applied the system for continuous ordering and separation of suspension particles.

  • 49. Rypdal, K.
    et al.
    Kozelov, B.
    Ratynskaia, Svetlana V.
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Klumov, B.
    Knapek, C.
    Rypdal, M.
    Scale-free vortex cascade emerging from random forcing in a strongly coupled system2008Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We elucidate the unifying aspects of self-organized criticality (SOC) and turbulence through analysis of data from a laboratory dusty plasma monolayer. We compare analysis of experimental data with simulations of a two-dimensional (2D) many-body system, of 2D chaotic fluid flow, and two different SOC-models, the Zhang and the Bak-Tang-Wiesenfeld (BTW) models, all subject to steady random forcing at small scales. The scale-free vortex cascade is apparent from structure functions as well as spatio-temporal avalanche analysis. We find similar scaling exponents for the experiment, the many-body simulation, and the fluid simulation, indicating some common dynamical features. However, the exponents of the Zhang model are different from those of the BTW model, and they are all different from those of the dust and fluid systems. Thus, we conclude that the dust monolayer dynamics can be viewed as turbulent as well as avalanching, but a fluid model is a better representation of the dust dynamics for this particular experiment than the sandpile models considered. The experiment exhibits global fluctuation statistics consistent with a recent hypothesis predicting universal non-Gaussian probability density functions, but the model systems yield this result only in a restricted range of forcing conditions.

  • 50.
    Schönecker, Stephan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. IFW Dresden, Germany.
    Richter, M.
    Koepernik, K.
    Eschrig, H.
    Prediction of first-order martensitic transitions in strained epitaxial films2015Inngår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 17, artikkel-id 023005Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Coherent epitaxial growth allows us to produce strained crystalline films with structures that are unstable in the bulk. Thereby, the overlayer lattice parameters in the interface plane, (a, b), determine the minimum-energy out-of-plane lattice parameter, cmin(a, b). We show by means of density-functional total energy calculations that this dependence can be discontinuous and predict related first-order phase transitions in strained tetragonal films of the elements V, Nb, Ru, La, Os, and Ir. The abrupt change of cmin can be exploited to switch properties specific to the overlayer material. This is demonstrated for the example of the superconducting critical temperature of a vanadium film which we predict to jump by 20% at a discontinuity of cmin.

12 1 - 50 of 62
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