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  • 651.
    Sellin, Karl A. H.
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    First order phase transition and tricritical point in multiband U(1) London superconductorsManuscript (preprint) (Other academic)
    Abstract [en]

    The order of the superconducting phase transition is a classical problem. Single-component type-2 superconductors exhibit a continuous "inverted-XY" phase transition, as was first demonstrated for U(1) lattice London superconductors by a celebrated duality mapping with subsequent backing by numerical simulations. Here we study this problem in multiband U(1) London superconductors and find evidence that by contrast the model has a tricritical point. The superconducting phase transition becomes first-order when the Josephson length is sufficiently large compared to the magnetic field penetration length. We present evidence that the fluctuation-induced dipolar interaction between vortex loops makes the phase transition discontinuous. We discuss that this mechanism is also relevant for the phase transitions in multicomponent gauge theories with higher broken symmetry.

  • 652.
    Sellin, Karl A. H.
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    First-order phase transition and tricritical point in multiband U(1) London superconductors2016In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 5, article id 054524Article in journal (Refereed)
    Abstract [en]

    The order of the superconducting phase transition is a classical problem. Single-component type-2 superconductors exhibit a continuous "inverted-XY" phase transition, as was first demonstrated for U(1) lattice London superconductors by a celebrated duality mapping with subsequent backing by numerical simulations. Here we study this problem in multiband U(1) London superconductors and find evidence that by contrast the model has a tricritical point. The superconducting phase transition becomes first order when the Josephson length is sufficiently large compared to the magnetic field penetration length. We present evidence that the fluctuation-induced dipolar interaction between vortex loops makes the phase transition discontinuous. We discuss that this mechanism is also relevant for the phase transitions in multicomponent gauge theories with higher broken symmetry.

  • 653.
    Sellin, Karl A. H.
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics. Department of Physics, University of Massachusetts, Amherst, MA 01003, United States .
    Stripe, gossamer, and glassy phases in systems with strong nonpairwise interactions2013In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 88, no 4, p. 042305-Article in journal (Refereed)
    Abstract [en]

    We study structure formation in systems of classical particles in two dimensions with long-range attractive short-range repulsive two-body interactions and repulsive three-body interactions. Stripe, gossamer, and glass phases are found as a result of nonpairwise interaction.

  • 654.
    Shaikh, Nabila
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Consequences of Violation of Special Relativity and Causality2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 655. Shin, Junsoo
    et al.
    Nascimento, Von Braun
    Geneste, Gregory
    Rundgren, John
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Plummer, E. Ward
    Dkhil, Brahim
    Kalinin, Sergei V.
    Baddorf, Arthur P.
    Atomistic Screening Mechanism of Ferroelectric Surfaces: An In Situ Study of the Polar Phase in Ultrathin BaTiO3 Films Exposed to H2O2009In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 9, no 11, p. 3720-3725Article in journal (Refereed)
    Abstract [en]

    The polarization screening mechanism and ferroelectric phase stability of ultrathin BaTiO3 films exposed to water molecules is determined by first principles theory and in situ experiment. Surface crystallography data from electron diffraction combined with density functional theory calculations demonstrate that small water vapor exposures do not affect surface structure or polarization. Large exposures result in surface hydroxylation and rippling, formation of surface oxygen vacancies, and reversal of the polarization direction. Understanding interplay between ferroelectric phase stability, screening, and atomistic processes at surfaces is a key to control low-dimensional ferroelectricity.

  • 656. Sierra, D. Aristizabal
    et al.
    Herrero-Garcia, Juan
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Restrepo, D.
    Vicente, A.
    Diboson anomaly: Heavy Higgs resonance and QCD vectorlike exotics2016In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 93, no 1, article id 015012Article in journal (Refereed)
    Abstract [en]

    The ATLAS Collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region 1.8-2.2 TeV. In light of these results, we argue that such a signal might be the first manifestation of the production and further decay of a heavy CP-even Higgs resulting from a type-I two Higgs doublet model. We demonstrate that in the presence of colored vectorlike fermions, its gluon fusion production cross section is strongly enhanced, with the enhancement depending on the color representation of the new fermion states. Our findings show that barring the color triplet case, any QCD "exotic" representation can fit the ATLAS result in fairly large portions of the parameter space. We have found that if the diboson excess is confirmed and this mechanism is indeed responsible for it, then the LHC Run-2 should find (i) a CP-odd scalar with mass below similar to 2.3 TeV, (ii) new colored states with masses below similar to 2 TeV, (iii) no statistically significant diboson events in the W(+/-)Z channel, (iv) events in the triboson channels W(+/-)W(-/+)Z and ZZZ with invariant mass amounting to the mass of the CP-odd scalar.

  • 657.
    Sigurdsson, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Silvestrov, Sergei
    Centre for Mathematical Sciences, Lund University.
    Lie Color and Hom-Lie Algebras of Witt Type and Their Central Extensions2009In: GENERALIZED LIE THEORY IN MATHEMATICS, PHYSICS AND BEYOND / [ed] Silvestrov S; Paal E; Abramov V; Stolin A, BERLIN: SPRINGER-VERLAG BERLIN , 2009, p. 247-255Conference paper (Refereed)
    Abstract [en]

    In this article, two classes of Gamma-graded Witt-type algebras, Lie color and hom-Lie algebras of Witt type, are considered. These algebras can be seen as generalizations of Lie algebras of Witt type. One-dimensional central extensions of Lie color and hom-Lie algebras of Witt type are investigated.

  • 658.
    Sigurdsson, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Silvestrov, Sergei D.
    Bosonic realizations of the colour Heisenberg Lie algebra2006In: Journal of Nonlinear Mathematical Physics, ISSN 1402-9251, E-ISSN 1776-0852, Vol. 13, p. 110-128Article in journal (Refereed)
    Abstract [en]

    We describe realizations of the colour analogue of the Heisenberg Lie algebra by power series in non-commuting indeterminates satisfying Heisenberg's canonical commutation relations of quantum mechanics. The obtained formulas are used to construct new operator representations of the colour Heisenberg Lie algebra. These representations are shown to be closely connected with some combinatorial identities and functional difference-differential interpolation formulae involving Euler numbers.

  • 659.
    Sigurdsson, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Silvestrov, Sergei D.
    Graded quasi-Lie algebras of Witt type2006In: Czechoslovak Journal of Physics, ISSN 0011-4626, E-ISSN 1572-9486, Vol. 56, no 10-11, p. 1287-1291Article in journal (Refereed)
    Abstract [en]

    In this article, we introduce a new class of graded algebras called quasi-Lie algebras of Witt type. These algebras can be seen as a generalization of other Witt-type algebras like Lie algebras of Witt type and their colored version, Lie color algebras of Witt type.

  • 660.
    Silaev, M. A.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Stable fractional flux vortices and unconventional magnetic state in two-component superconductors2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 14, p. 144519-Article in journal (Refereed)
    Abstract [en]

    In the framework of London theory we study the unconventional magnetic state in two-component superconductors with a finite density of fractional flux vortices stabilized near the surface. We show that the process of vortex entry into the two-component superconductor consists of several steps, while the external magnetic field increases from zero. At the first stage only vortices in one of the order parameter components penetrate and sit at the equilibrium position near the surface. When the magnetic field is increased further, vortices in the second-order parameter component eventually enter the superconductor. Such a complex partial vortex penetration leads to the modification of a Bean-Livingston barrier and a magnetization curve as compared to conventional single-component superconductors. We discuss the possibility of experimental identification of protonic superconductivity in the projected superconducting state of liquid metallic hydrogen and hydrogen-rich alloys with the help of the partial vortex penetration effect.

  • 661.
    Silaev, Mihail A.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Dissipative Vortex Motion in Fermi Superfluids at Ultra Low Temperatures2013In: Journal of Low Temperature Physics, ISSN 0022-2291, E-ISSN 1573-7357, Vol. 171, no 5-6, p. 539-550Article in journal (Refereed)
    Abstract [en]

    We discuss in detail the recently proposed mechanism of dissipation and damping of the vortex motion in Fermi superfluids at temperatures much smaller than the critical one (Silaev, Phys. Rev. Lett., 108:045303, 2012). In the absence of the heat bath of normal component the kinetic energy of the superflow is transferred to the vortex core fermions due to the accelerated vortex motion. The resulting local heating of the vortex cores creates the heat flux carried by non-equilibrium quasiparticles emitted by moving vortices. Here we study this peculiar kinetics of localized quasiparticles beyond relaxation time approximation, calculate the decrement of Kelvin waves and the total power losses in Kelvin wave cascade realized by the turbulent motion of He-3-B.

  • 662.
    Silaev, Mihail A.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Universal Mechanism of Dissipation in Fermi Superfluids at Ultralow Temperatures2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, no 4, p. 045303-Article in journal (Refereed)
    Abstract [en]

    We show that the vortex dynamics in Fermi superfluids at ultralow temperatures is governed by the local heating of the vortex cores creating the heat flux carried by nonequilibrium quasiparticles emitted by moving vortices. This mechanism provides a universal zero temperature limit of dissipation in Fermi superfluids. For the typical experimental conditions realized by the turbulent motion of He-3-B, the temperature of the vortex cores is estimated to be of the order 0.2T(c). The dispersion of Kelvin waves is derived, and the heat flow generated by Kelvin cascade is shown to have a value close to that experimentally observed.

  • 663.
    Silaev, Mihail
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Microscopic derivation of two-component Ginzburg-Landau model and conditions of its applicability in two-band systems2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, no 13, p. 134514-Article in journal (Refereed)
    Abstract [en]

    We report a microscopic derivation of two-component Ginzburg-Landau (GL) field theory and the conditions of its validity in two-band superconductors. We also investigate the conditions when microscopically derived or phenomenological GL models fail and one should resort to a microscopic description. We show that besides being directly applicable at elevated temperatures, a version of a minimal two-component GL theory in certain cases also gives an accurate description of certain aspects of a two-band system, even substantially far from T-c. This shows that a two-component GL model can be used for addressing a wide range of questions in multiband systems, in particular vortex physics and magnetic response. We also argue that a single Ginzburg-Landau parameter cannot in general characterize the magnetic response of multiband systems.

  • 664.
    Silaev, Mihail
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Microscopic theory of type-1.5 superconductivity in multiband systems2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 9, p. 094515-Article in journal (Refereed)
    Abstract [en]

    We report a self-consistent microscopic theory of characteristic length scales, vortex structure, and type-1.5 superconducting state in two-band systems using two-band Eilenberger formalism.

  • 665.
    Silaev, Mihail
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Unusual mechanism of vortex viscosity generated by mixed normal modes in superconductors with broken time reversal symmetry2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, no 22, p. 220504-Article in journal (Refereed)
    Abstract [en]

    We show that under certain conditions, multiband superconductors with broken time reversal symmetry have a vortex viscosity-generating mechanism which is different from that in conventional superconductors. It appears due to the existence of a mixed superfluid phase-density mode inside the vortex core. This contribution is dominant near the time reversal symmetry-breaking phase transition. The results could be relevant for the three-band superconductor Ba1-xKxFe2As2.

  • 666.
    Silaev, Mihail
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Statistical Physics.
    Garaud, Julien
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics. KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Phase diagram of dirty two-band superconductors and observability of impurity-induced s plus i s state2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 2, article id 024517Article in journal (Refereed)
    Abstract [en]

    We investigate the phase diagram of dirty two-band superconductors. This paper primarily focuses on the properties and observability of the time-reversal symmetry-breaking s + is superconducting states, which can be generated in two-band superconductors by interband impurity scattering. We show that such states can appear in two distinct ways. First, according to a previously discussed scenario, the s + is state can form as an intermediate phase at the impurity-driven crossover between s(+/-) and s(++) states. We show that there is a second scenario where domains of the s + is state exists in the form of an isolated dome inside the s(+/-) domain, completely detached from the transition between s(+/-) and s(++) states. We demonstrate that in both cases the s + is state generated by impurity scattering exists in an extremely small interval of impurity concentrations. Although this likely precludes direct experimental observation of the s + is state formation due to this mechanism, this physics leads to the appearance of a region inside both the s(+/-) and s(++) domains with unusual properties due to softening of normal modes.

  • 667.
    Silaev, Mihail
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Garaud, Julien
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Unconventional thermoelectric effect in superconductors that break time-reversal symmetry2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 17, article id 174510Article in journal (Refereed)
    Abstract [en]

    We demonstrate that superconductors that break time-reversal symmetry can exhibit thermoelectric properties, which are entirely different from the Ginzburg mechanism. As an example, we show that in the s + is superconducting state there is a reversible contribution to thermally induced supercurrent, whose direction is not invariant under time-reversal operation. Moreover in contrast to Ginzburg mechanism it has a singular behavior near the time-reversal symmetry breaking phase transition. The effect can be used to confirm or rule out the s + is state, which is widely expected to be realized in pnictide compounds Ba1-xKxFe2As2 and stoichiometric LiFeAs.

  • 668.
    Silaev, Mihail
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics. Aalto Univ, Finland.
    Heikkila, Tero T.
    Virtanen, Pauli
    Lindblad-equation approach for the full counting statistics of work and heat in driven quantum systems2014In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 90, no 2, p. 022103-Article in journal (Refereed)
    Abstract [en]

    We formulate the general approach based on the Lindblad equation to calculate the full counting statistics of work and heat produced by driven quantum systems weakly coupled with a Markovian thermal bath. The approach can be applied to a wide class of dissipative quantum systems driven by an arbitrary force protocol. We show the validity of general fluctuation relations and consider several generic examples. The possibilities of using calorimetric measurements to test the presence of coherence and entanglement in the open quantum systems are discussed.

  • 669.
    Silaev, Mihail
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics. Aalto University, Finland.
    Virtanen, P.
    Bergeret, F. S.
    Heikkila, T. T.
    Long-Range Spin Accumulation from Heat Injection in Mesoscopic Superconductors with Zeeman Splitting2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, no 16, article id 167002Article in journal (Refereed)
    Abstract [en]

    We describe far-from-equilibrium nonlocal transport in a diffusive superconducting wire with a Zeeman splitting, taking into account different spin relaxation mechanisms. We demonstrate that due to the Zeeman splitting, an injection of current in a superconducting wire creates spin accumulation that can only relax via thermalization. This effect leads to a long-range spin accumulation detectable in the nonlocal signal. Our model gives a qualitative explanation and provides accurate fits of recent experimental results in terms of realistic parameters.

  • 670.
    Silaev, Mihail
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics. Aalto Univ, OV Lounasmaa Lab, Finland.
    Virtanen, P.
    Heikkila, T. T.
    Bergeret, F. S.
    Spin Hanle effect in mesoscopic superconductors2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 2, p. 024506-Article in journal (Refereed)
    Abstract [en]

    We present a theoretical study of spin transport in a superconducting mesoscopic spin valve under the action of a magnetic field misaligned with respect to the injected spin. We demonstrate that superconductivity can either strongly enhance or suppress the coherent spin rotation, depending on the type of spin relaxation mechanism being dominated either by spin-orbit coupling or spin-flip scattering at impurities. We also predict a subgap contribution to the nonlocal conductance in multiterminal superconducting hybrid structures which completely eliminates the effect of spin rotation at sufficiently low temperatures.

  • 671.
    Silaev, Mikhail
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Magnetic behavior of dirty multiband superconductors near the upper critical field2016In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 21, article id 214509Article in journal (Refereed)
    Abstract [en]

    Magnetic properties of dirty multiband superconductors near the upper critical field are studied. The parameter kappa(2) characterizing magnetization slope is shown to have a significant temperature variation which is quite sensitive to the pairing interactions and relative strengths of intraband impurity scattering. In contrast to single-band superconductors the increase of kappa(2) at low temperatures can be arbitrarily large determined by the ratio of maximal and minimal diffusion coefficients in different bands. Temperature dependencies of kappa(2)(T) in two-band MgB2 and iron-based superconductors are shown to be much more sensitive to the multiband effects than the upper critical field H-c2(T).

  • 672.
    Silaev, Mikhail A.
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Thuneberg, E. V.
    Fogelstrom, M.
    Lifshitz Transition in the Double-Core Vortex in He-3-B2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 115, no 23, article id 235301Article in journal (Refereed)
    Abstract [en]

    We study the spectrum of fermion states localized within the vortex core of a weak-coupling p-wave superfluid. The low energy spectrum consists of two anomalous branches that generate a large density of states at the locations of the half cores of the vortex. Fermi liquid interactions significantly stretch the vortex structure, which leads to a Lifshitz transition in the effective Fermi surface of the vortex core fermions. We apply the results to the rotational dynamics of vortices in superfluid He-3-B and find an explanation for the observed slow mode.

  • 673. Sirtl, T.
    et al.
    Jelic, J.
    Meyer, J.
    Das, K.
    Heckl, W. M.
    Moritz, W.
    Rundgren, John
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theory of Materials.
    Schmittel, M.
    Reuter, K.
    Lackinger, M.
    Adsorption structure determination of a large polyaromatic trithiolate on Cu(111): Combination of LEED-I(V) and DFT-vdW2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 26, p. 11054-11060Article in journal (Refereed)
    Abstract [en]

    The adsorption geometry of 1,3,5-tris(4-mercaptophenyl)benzene (TMB) on Cu(111) is determined with high precision using two independent methods, experimentally by quantitative low energy electron diffraction (LEED-I(V)) and theoretically by dispersion corrected density functional theory (DFT-vdW). Structural refinement using both methods consistently results in similar adsorption sites and geometries. Thereby a level of confidence is reached that allows deduction of subtle structural details such as molecular deformations or relaxations of copper substrate atoms.

  • 674.
    Sivertsson, Sofia
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Dark matter in and around stars2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is by now compelling evidence that most of the matter in the universe is in the form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models dark matter particles can annihilate with each other into standard model particles. The direct or indirect observation of such annihilation products could give important clues for the dark matter puzzle. For signals from dark matter annihilations to be detectable, typically high dark matter densities are required. Massive objects, such as stars, can increase the local dark matter density both via scattering off nucleons and by pulling in dark matter gravitationally as the star forms. Dark matter annihilations outside the star would give rise to gamma rays and this is discussed in the first paper. Furthermore dark matter annihilations inside the star would deposit energy inside the star which, if abundant enough, could alter the stellar evolution. Aspects of this are investigated in the second paper. Finally, local dark matter overdensities formed in the early universe could still be around today; prospects of detecting gamma rays from such clumps are discussed in the third paper.

  • 675.
    Sivertsson, Sofia
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Studies of dark matter in and around stars2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is by now compelling evidence that most of the matter in the Universe is in the form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models, dark matter particles can annihilate with each other into standard model particles; the direct or indirect observation of such annihilation products could give important clues for the dark matter puzzle. For signals from dark matter annihilations to be detectable, typically high dark matter densities are required. Massive objects, such as stars, can increase the local dark matter density both via scattering off nucleons and by pulling in dark matter gravitationally as a star forms. Annihilations within this kind of dark matter population gravitationally bound to a star, like the Sun, give rise to a gamma ray flux. For a star which has a planetary system, dark matter can become gravitationally bound also through gravitational interactions with the planets. The interplay between the different dark matter populations in the solar system is analyzed, shedding new light on dark matter annihilations inside celestial bodies and improving the predicted experimental reach. Dark matter annihilations inside a star would also deposit energy in the star which, if abundant enough, could alter the stellar evolution. This is investigated for the very first stars in the Universe. Finally, there is a possibility for abundant small scale dark matter overdensities to have formed in the early Universe. Prospects of detecting gamma rays from such minihalos, which have survived until the present day, are discussed.

  • 676.
    Sivertsson, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Edsjö, Joakim
    Department of Physics, Stockholm University.
    Accurate calculations of the WIMP halo around the Sun and prospects for gamma ray detection2008In: Identification of dark matter 2008: idm2008, SISSA , 2008, p. 112-Conference paper (Refereed)
    Abstract [en]

    Weakly interacting massive particles (WIMPs) can be captured by heavenly objects, like the Sun.Under the process of being captured by the Sun, they will build up a population of WIMPs aroundit, that will eventually sink to the core of the Sun. It has been argued with simpler estimatesbefore that this halo of WIMPs around the Sun could be a strong enough gamma ray source to bea detectable signature for WIMP dark matter. We here revisit the problem using detailed MonteCarlo simulations and detailed composition and structure information about the Sun to estimatethe size of the gamma ray flux. Compared to earlier estimates, we find that the gamma ray fluxfrom WIMP annihilations in the Sun halo would be negligible and no current or planned detectorswould even be able to detect this flux.

  • 677.
    Sivertsson, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Edsjö, Joakim
    Accurate calculations of the WIMP halo around the Sun and prospects for its gamma-ray detection2010In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 81, no 6, p. 063502-1-063502-14Article in journal (Refereed)
    Abstract [en]

    Galactic weakly interacting massive particles (WIMPs) may scatter off solar nuclei to orbits gravitationally bound to the Sun. Once bound, the WIMPs continue to lose energy by repeated scatters in the Sun, eventually leading to complete entrapment in the solar interior. While the density of the bound population is highest at the center of the Sun, the only observable signature of WIMP annihilations inside the Sun is neutrinos. It has been previously suggested that although the density of WIMPs just outside the Sun is lower than deep inside, gamma rays from WIMP annihilation just outside the surface of the Sun, in the so-called WIMP halo around the Sun, may be more easily detected. We here revisit this problem using detailed Monte Carlo simulations and detailed composition and structure information about the Sun to estimate the size of the gamma-ray flux. Compared to earlier simpler estimates, we find that the gamma-ray flux from WIMP annihilations in the solar WIMP halo would be negligible; no current or planned detectors would be able to detect this flux.

  • 678.
    Sivertsson, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Edsjö, Joakim
    Stockholm University.
    WIMP diffusion in the Solar System including solar WIMP-nucleon scattering2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, no 12, p. 123514-Article in journal (Refereed)
    Abstract [en]

    Dark matter in the form of Weakly Interacting Massive Particles (WIMPs) can be captured by the Sun and the Earth, sink to their cores, annihilate and produce neutrinos that can be searched for with neutrino telescopes. The calculation of the capture rates of WIMPs in the Sun and especially the Earth are affected by large uncertainties coming mainly from effects of the planets in the Solar System, reducing the capture rates by up to an order of magnitude (or even more in some cases). We show that the WIMPs captured by weak scatterings in the Sun also constitute an important bound WIMP population in the Solar System. Taking this population and its interplay with the population bound through gravitational diffusion into account cancel the planetary effects on the capture rates, and the capture essentially proceeds as if the Sun and the Earth were free in the galactic halo. The neutrino signals from the Sun and the Earth are thus significantly higher than claimed in the scenarios with reduced capture rates.

  • 679.
    Sivertsson, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Gandolo, Paolo
    The WIMP capture process for dark stars in the early universe2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 729, no 1, p. 51-1-51-11Article in journal (Refereed)
    Abstract [en]

    The first stars to form in the universe may have been dark stars, powered by dark matter annihilation instead of nuclear fusion. The initial amount of dark matter gathered by the star gravitationally can sustain it only for a limited period of time. It has been suggested that capture of additional dark matter from the environment can prolong the dark star phase even to the present day. Here we show that this capture process is ineffective to prolong the life of the first generation of dark stars. We construct a Monte-Carlo simulation that follows each Weakly Interacting Massive Particle (WIMP) in the dark matter halo as its orbit responds to the formation and evolution of the dark star, as it scatters off the star's nuclei, and as it annihilates inside the star. A rapid depletion of the WIMPs on orbits that cross the star causes the demise of the first generation of dark stars. We suggest that a second generation of dark stars may in principle survive much longer through capture. We comment on the effect of relaxing our assumptions.

  • 680. Skorodumova, N. V.
    et al.
    Belonoshko, Anatoly B.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Huang, L.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Johansson, Börje
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Stability of the MgCO3 structures under lower mantle conditions2005In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 90, no 06-maj, p. 1008-1011Article in journal (Refereed)
    Abstract [en]

    The presence of carbon in the Earth makes the search for high-pressure carbon-containing phases essential for our understanding of mineral compositions of the Earth's mantle. In a recent study Isshiki et al. (2004) demonstrated that magnesite transforms into a new phase at lower mantle pressures. However, the structure of the emerging phase remained unknown. Here we show, by means of first principles calculations, that MgCO3 magnesite can transform into a pyroxene structure at 113 GPa, which further transforms into a CaTiO3-type structure at about 200 GPa.

  • 681.
    Sundholm, Joel
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    The entropy of frustrated Ising systems calculated using Monte Carlo methods.2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 682.
    Sundin, Martin
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
    Aspects of extra dimensions and membranes2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is about thwo papers related to extra dimensions. Paper A discusses extrinsic curvature effects, and paper B treats symmetries of supersymmetric membranes.

    In the part of this thesis related to paper A, we extend the theory of non-relativistic quantum particles confined to submanifolds to relativistic boson fields. We show that a Klein-Gordon field constrained to a submanifold of a Lorentzian manifold experiences an induced potential similar to the one for the Schr{\"o}dinger equation. We embedd the Schwarzschild solution and the Robertson-Walker space-time and derive the induced potentials. Possible physical consequences of these induced potentials are also discussed.

    The second part is related to paper B, we study the dynamics of supersymmetric membranes, which are higher dimensional generalizations of supersymmetric strings. We derive a supersymmetric analogue of a dynamical symmetry for bosonic membranes.

  • 683.
    Swing, André
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Experimental Tests of General Relativity2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    This paper treats Einstein's theory of General Relativity (GR), in particular three of the

    earliest experiments testing its validity. It covers the de ection of, and the redshift of

    light in a gravity eld, two new phenomena predicted by GR. The perihelion precession

    of the planet Mercury and how GR matches observations of it more correctly than classic

    physics is also covered. In addition to the three older tests above, the more modern

    application in the GPS system is discussed, and how it can be regarded as a test of GR.

    Some theoretical questions are also discussed, including comparing classic physics to GR

    and the classical limit of GR.

  • 684.
    Söderstrand, Alexander
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Wiberg, Magnus
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    A simulation of fluid flow in the square and simple cubic lattices with invasion percolation2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Descriptions of the propagation of a fluid in a porous structure with percolation theory led to the introduction of invasion percolation. Invasion percolation is significantly different from ordinary percolation which is why its fractal characteristics can differ from ordinary percolation. Rules can be invoked on a percolation model and it is of interest to investigate their influence on the behaviour of the percolation. In this paper simulations of invasion percolation have been carried out in square and cubic lattices and fractal dimensions have been calculated numerically from the acquired simulation data. A rule called trapping have been invoked on invasion percolation model and was found to be affecting the result significantly in two dimensions. Without the trapping rule, similarities to ordinary percolation was found. In three dimensional lattices the effect of this rule diminished to almost insignificant levels and similarities to ordinary percolation was found regardless the trapping rule.

  • 685.
    Theveniaut, Hugo
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Vojta, Matthias
    Bound states of fractionalized excitations in a modulated Kitaev spin liquid2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 5, article id 054401Article in journal (Refereed)
    Abstract [en]

    Fractionalization is a hallmark of spin-liquid behavior; it typically leads to response functions consisting of continua instead of sharp modes. However, microscopic processes can enable the formation of short-distance bound states of fractionalized excitations, despite asymptotic deconfinement. Here we study such bound-state formation for the Z(2) spin liquid realized in Kitaev's honeycomb compass model, supplemented by a kekule distortion of the lattice. Bound states between flux pairs andMajorana fermions form in theMajorana band gaps. We calculate the dynamic spin susceptibility and show that bound states lead to sharp modes in the magnetic response of the spin liquid, with the momentum dependence of the corresponding spectral weight encoding the internal symmetry of the bound state. As a byproduct, we also show that isolated fluxes may produce Majorana bound states at exactly zero energy. Generalizations and implications of the results are discussed.

  • 686. Tinnacher, Ruth M.
    et al.
    Holmboe, Michael
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Davis, James A.
    Tournassat, Christophe
    Bourg, Ian
    Impacts of pore structure and diffusion-accessible porosity for calcium-bromide diffusion in sodium-montmorillonite2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Article in journal (Other academic)
  • 687.
    Tjörnhammar, Richard
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics. KTH, School of Biotechnology (BIO), Centres, KTH-USTC Joint Center for Bio- and Nano-Materials.
    A first-principles study on the electronic structure ofone-dimensional [TM(Bz)]∞ polymer(TM= Y, Zr, Nb, Mo, and Tc)2009In: Frontiers of Physics in China, ISSN 1673-3487, E-ISSN 1673-3606, Vol. 4, no 3, p. 403-407Article in journal (Refereed)
    Abstract [en]

    A systematic density functional theory (DFT) study has been performed to investigate the electronicand magnetic properties of one-dimensional sandwich polymers constructed with benzene (Bz) and thesecond-row transition metal (TM = Y, Zr, Nb, Mo, and Tc). Within the framework of generalized gra-dient approximation (GGA), [Tc(Bz)]∞ is a ferromagnetic half-metal, and [Nb(Bz)]∞ is a ferromagneticmetal. With the on-site Coulomb interaction for 4d TM atoms being taken into account, [Tc(Bz)]∞keeps a robust half-metallic behavior, while [Nb(Bz)]∞ becomes a spin-selective semiconductor. Thestability of the half-metallic [Tc(Bz)]∞ polymer is discussed based on magnetic anisotropy energy(MAE). Compared with 0.1 meV per metal atom in [Mn(Bz)]∞ , the calculated MAE for [Tc(Bz)]∞ is2.3 meV per metal atom. Such a significantly larger MAE suggests that Tc(Bz)]∞ is practically morepromising than its first-row TM equivalent.

  • 688.
    Tjörnhammar, Richard
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Classical and Quantum Descriptions of Proteins, Lipids and Membranes2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis the properties of proteins and membranes are studied by molecular dynamics simulations. The subject is decomposed into parts addressing free energy calculations in proteins, mechanical inclusion models for lipid bilayers, phase transitions and structural correlations in lipid bilayers and atomistic lipid bilayer models. The work is based on results from large scale computer simulations, quantum mechanical and continuum models. Efficient statistical sampling and the coarseness of the models needed to describe the ordered and disordered states are of central concern.

    Classical free energy calculations of zinc binding, in metalloproteins, require a quantum mechanical correction in order to obtain realistic binding energies. Classical electrostatic polarisation will influence the binding energy in a large region surrounding the ion and produce reasonable equilibrium structures in the bound state, when compared to experimental evidence.

    The free energy for inserting a protein into a membrane is calculated with continuum theory. The free energy is assumed quadratic in the mismatch and depend on two elastic constants of the membrane. Under these circumstances, the free energy can then be written as a line tension multiplied by the circumference of the membrane inclusion. The inclusion model and coarse grained particle simulations of the membranes show that the thickness profile around the protein will be an exponentially damped oscillation.

    Coarse-grained particle simulations of model membranes containing mixtures of phospholipid and cholesterol molecules at different conditions were performed. The gel-to-liquid crystalline phase transition is successively weakened with increasing amounts of cholesterol without disappearing even at a concentration of cholesterol as high as 60%.

    A united atom parameterization of diacyl lipids was constructed. The aim was to construct a new force field that retains and improves the good agreement for the fluid phase and at the same time produces a gel phase at low temperatures, with properties coherent with experimental findings. The global bilayer tilt obtains an azimuthal value of 31and is aligned between lattice vectors in the bilayer plane. It is also shown that the model yield a correct heat of melting as well as heat capacities in the fluid and gel phase of DPPC.

     

  • 689.
    Tjörnhammar, Richard
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Edholm, Olle
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Molecular dynamics simulations of Zn2+ coordination in protein binding sites2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 132, no 20, p. 205101-Article in journal (Refereed)
    Abstract [en]

    A systematic molecular dynamics (MD) study of zinc binding to a peptide that mimics the structural binding site of horse liver alcohol dehydrogenase (HLADH) has been conducted. The four zinc binding cysteines were successively mutated into alanines to study the stability, zinc coordination, and free energy of binding. The zinc ion is coordinated to four sulfurs in the native peptide as in x-ray structures of HLADH. When the cysteines are replaced by alanines, the zinc coordinating sulfurs are replaced by waters and/or polypeptide backbone carbonyl oxygens. With two or fewer cysteines, the coordination number increases from four to six, while the coordination number varies between four and six with three cysteines depending on which of the cysteines that is replaced by an alanine. The binding free energies of zinc to the proteins were calculated from MD free energy integration runs to which corrections from quantum mechanical cluster calculations were added. There is a reasonable correlation with experimental binding free energies [T. Bergman , Cell. Mol. Life Sci. 65, 4019 (2008)]. For the chains with the lowest structural fluctuations and highest free energies lower coordination numbers for zinc are obtained. Finally, x-ray absorption fine structure spectra were calculated from the MD structures.

  • 690.
    Tjörnhammar, Richard
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Edholm, Olle
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Reparameterized united atom model for molecular dynamics simulations of gel and fluid phosphatidylcholine bilayers2014In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 10, no 12, p. 5706-5715Article in journal (Refereed)
    Abstract [en]

    A new united atom parametrization of diacyl lipids like dipalmitoylphosphatidylcholine (DPPC) and the dimyristoylphosphatidylcholine (DMPC) has been constructed based on ab initio calculations to obtain fractional charges and the dihedral potential of the hydrocarbon chains, while the Lennard-Jones parameters of the acyl chains were fitted to reproduce the properties of liquid hydrocarbons. The results have been validated against published experimental X-ray and neutron scattering data for fluid and gel phase DPPC. The derived charges of the lipid phosphatidylcholine (PC) headgroup are shown to yield dipole components in the range suggested by experiments. The aim has been to construct a new force field that retains and improves the good agreement for the fluid phase and at the same time produces a gel phase at low temperatures, with properties coherent with experimental findings. The gel phase of diacyl-PC lipids forms a regular triangular lattice in the hydrocarbon region. The global bilayer tilt obtains an azimuthal value of 31 degrees and is aligned between lattice vectors in the bilayer plane. We also show that the model yields a correct heat of melting as well as decent heat capacities in the fluid and gel phase of DPPC.

  • 691.
    Tjörnhammar, Richard
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Edholm, Olle
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    The shape and free energy of a lipid bilayer surrounding a membrane inclusion2013In: Chemistry and Physics of Lipids, ISSN 0009-3084, E-ISSN 1873-2941, Vol. 169, p. 2-8Article in journal (Refereed)
    Abstract [en]

    Membrane inclusion interactions are studied within the scope of continuum theory. We show that the free energy functional for the membrane thickness can be rewritten as a constant times a dimensionless integral. For cylindrical inclusions, the resulting differential equation gives a thickness profile that depends on the radius of the cylinder and one single lipid property, a correlation length that is determined by the ratio of the thickness compressibility and bending moduli. The solutions decay in a non-monotonic fashion with one single observable minimum. A solution for planar geometry may either be explicitly constructed or obtained by letting the radius of the cylinder go to infinity. In dimensionless units the initial derivative of the thickness profile is universal and equal to -1/root 2 In physical units, the derivative depends on the size of the hydrophobic mismatch as well as the membrane correlation length and will usually be fairly small but clearly non-zero. The line tension between the protein inclusion and a fluid phase membrane will depend on the hydrophobic mismatch and be of the order of 10 pN (larger for the gel phase). This results in free energy costs for the inclusion that will be up to tens of kJ/mol (in the fluid phase).

  • 692.
    Tjörnhammar, Richard
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Edholm, Olof
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Atomistic Simulations of Gel and Liquid Crystalline Lipid Bilayers2014In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 106, no 2, p. 403A-403AArticle in journal (Other academic)
  • 693.
    Tjörnhammar, Richard O.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Biological Physics.
    Clustering Method in QMMM Modeling of the HLADH Binding Site2010In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 98, no 3, p. 39A-39AArticle in journal (Other academic)
  • 694. Tsygankov, Denis
    et al.
    Linden, Martin
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Fisher, Michael E.
    Back-stepping, dwell times, and hidden substeps in molecular motors2007In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, p. 496A-497AArticle in journal (Other academic)
  • 695. Tupitsyn, I. S.
    et al.
    Prokofiev, Nikolay
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Stability of Dirac Liquids with Strong Coulomb Interaction2017In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 118, no 2, article id 026403Article in journal (Refereed)
    Abstract [en]

    We develop and apply the diagrammatic Monte Carlo technique to address the problem of the stability of the Dirac liquid state (in a graphene-type system) against the strong long-range part of the Coulomb interaction. So far, all attempts to deal with this problem in the field-theoretical framework were limited either to perturbative or random phase approximation and functional renormalization group treatments, with diametrically opposite conclusions. Our calculations aim at the approximation-free solution with controlled accuracy by computing vertex corrections from higher-order skeleton diagrams and establishing the renormalization group flow of the effective Coulomb coupling constant. We unambiguously show that with increasing the system size L (up to ln(L)∼40), the coupling constant always flows towards zero; i.e., the two-dimensional Dirac liquid is an asymptotically free T=0 state with divergent Fermi velocity.

  • 696. Tupitsyn, Igor S.
    et al.
    Mishchenko, Andrey S.
    Nagaosa, Naoto
    Prokof'ev, Nikolay
    KTH, School of Engineering Sciences (SCI), Theoretical Physics. University of Massachusetts, United States.
    Coulomb and electron-phonon interactions in metals2016In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 15, article id 155145Article in journal (Refereed)
    Abstract [en]

    An accurate and consistent theory of phonons in metals requires that all long-range Coulomb interactions between charged particles (electrons and ions) be treated on equal footing. So far, all attempts to deal with this nonperturbative system were relying on uncontrolled approximations in the absence of small parameters. In this paper, we develop the diagrammatic Monte Carlo approach for a two-component Coulomb system that obtains the solution to this fundamental problem in an approximation-free way by computing vertex corrections from higher-order skeleton graphs. The feasibility of the method is demonstrated by calculating the spectrum of longitudinal acoustic phonons in a simple cubic lattice, determining their sound velocity, and obtaining the phonon spectral densities by analytic continuation of the Matsubara-Green's functions. Final results are checked against the lowest-order fully self-consistent GW approximation in both adiabatic and nonadiabatic regimes.

  • 697.
    Twengström, Mikael
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Adler, Jonas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Quantum contributions to the molar heat capacity of diatomic gases2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 698.
    Ullmann, R. T.
    et al.
    MPI Biophys, Theoret & Computat Biophys, Gottingen, Germany..
    Kutzner, C.
    MPI Biophys, Theoret & Computat Biophys, Gottingen, Germany..
    Beckmann, A.
    Julich Supercomp Ctr, IAS, Div Math, Julich, Germany..
    Kohnke, B.
    MPI Biophys, Theoret & Computat Biophys, Gottingen, Germany..
    Kabadashow, I.
    Julich Supercomp Ctr, IAS, Div Math, Julich, Germany..
    Dachsel, H.
    Julich Supercomp Ctr, IAS, Div Math, Julich, Germany..
    Hess, Berk
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Grubmueller, H.
    MPI Biophys, Theoret & Computat Biophys, Gottingen, Germany..
    GromEx: Electrostatics with chemical variability for realistic molecular simulations on the exascale2015In: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 44, p. S145-S145Article in journal (Other academic)
  • 699.
    Unnersjö Jess, David
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    On superluminal particles, tachyons, and a discussion on their existence2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 700. Urba, Laura
    et al.
    Lundh, Emil
    Rosengren, Anders
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    One-dimensional extended Bose-Hubbard model with a confining potential: a DMRG analysis2006In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 39, no 24, p. 5187-5198Article in journal (Refereed)
    Abstract [en]

    The extended Bose-Hubbard model in a quadratic trap potential is studied using a finite-size density-matrix renormalization group method (DMRG). We compute the boson density profiles, the local compressibility and the hopping correlation functions. We observe the phase separation induced by the trap in all the quantities studied and conclude that the local density approximation is valid in the extended Bose-Hubbard model. From the plateaus obtained in the local compressibility it was possible to obtain the phase diagram of the homogeneous system which is in agreement with previous results.

111213141516 651 - 700 of 764
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