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  • 1.
    Abraham, Mark James
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Murtola, T.
    Schulz, R.
    Páll, Szilárd
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Smith, J. C.
    Hess, Berk
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Gromacs: High performance molecular simulations through multi-level parallelism from laptops to supercomputers2015In: SoftwareX, ISSN 2352-7110, Vol. 1-2, p. 19-25Article in journal (Refereed)
    Abstract [en]

    GROMACS is one of the most widely used open-source and free software codes in chemistry, used primarily for dynamical simulations of biomolecules. It provides a rich set of calculation types, preparation and analysis tools. Several advanced techniques for free-energy calculations are supported. In version 5, it reaches new performance heights, through several new and enhanced parallelization algorithms. These work on every level; SIMD registers inside cores, multithreading, heterogeneous CPU-GPU acceleration, state-of-the-art 3D domain decomposition, and ensemble-level parallelization through built-in replica exchange and the separate Copernicus framework. The latest best-in-class compressed trajectory storage format is supported.

  • 2.
    Aceituno Chavez, David
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Autocorrelation analysis on a 3D Ising model near the phase transition2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 3.
    Aceituno Chavez, David
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Melting of Striped Phases on the 2D Square Lattice2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 4.
    Aceituno, David
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Melting of Striped Phases on the 2D Square Lattice2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 5. Agarwalla, Sanjib Kumar
    et al.
    Choubey, Sandhya
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics. Harish-Chandra Research Institute, India .
    Prakash, Suprabh
    Probing neutrino oscillation parameters using high power superbeam from ESS2014In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 12, p. 020-Article in journal (Refereed)
    Abstract [en]

    A high-power neutrino superbeam experiment at the ESS facility has been proposed such that the source-detector distance falls at the second oscillation maximum, giving very good sensitivity towards establishing CP violation. In this work, we explore the comparative physics reach of the experiment in terms of leptonic CP-violation, precision on atmospheric parameters, non-maximal theta(23), and its octant for a variety of choices for the baselines. We also vary the neutrino vs. the anti-neutrino running time for the beam, and study its impact on the physics goals of the experiment. We find that for the determination of CP violation, 540 km baseline with 7 years of nu and 3 years of (v) over bar (7v + 3 (v) over bar) run-plan performs the best and one expects a 5 sigma sensitivity to CP violation for 48% of true values of delta (CP). The projected reach for the 200 km baseline with 7v + 3 (v) over bar run-plan is somewhat worse with 5 sigma sensitivity for 34% of true values of delta(CP). On the other hand, for the discovery of a non-maximal theta(23) and its octant, the 200 km baseline option with run-plan performs significantly better than the other baselines. A 5 sigma determination of a non-maximal theta(23) can be made if the true value of sin(2) theta(23) less than or similar to 0.45 or sin(2) theta(23) greater than or similar to 0.57. The octant of theta(23) could be resolved at 5 sigma if the true value of sin(2) theta(23) less than or similar to 0.43 or greater than or similar to 0.59, irrespective of delta(CP).

  • 6. Agarwalla, S.K.
    et al.
    Akhmedov, E.
    Blennow, Mattias
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Coloma, P.
    Donini, A.
    Fernandez-Martinez, E.
    Giunti, C.
    Gomez-Cadenas, J.J.
    Gonzalez-Garcia, M.C.
    Hernandez, P.
    Huber, P.
    Laveder, M.
    Li, T.
    Longhin, A.
    Lopez-Pavon, J.
    Maltoni, M.
    Meloni, D.
    Mena, O.
    Menendez, J.
    Mezzetto, M.
    Migliozzi, P.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Orme, C.
    Pascoli, S.
    Salvado, J.
    Schwetz, T.
    Scotto-Lavina, L.
    Tang, J.
    Terranova, F.
    Winter, W.
    Zhang, H.
    EUROnu-WP6 2010 Report2012Report (Other academic)
    Abstract [en]

    This is a summary of the work done by the Working Package 6 (Physics) of the EU project "EUROnu" during the second year of activity of the project.

  • 7. Agterberg, Daniel F.
    et al.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics. University of Massachusetts, USA.
    Garaud, Julien
    KTH, School of Engineering Sciences (SCI), Theoretical Physics. University of Massachusetts, USA.
    Microscopic prediction of skyrmion lattice state in clean interface superconductors2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 6, p. 064509-Article in journal (Refereed)
    Abstract [en]

    When an in-plane field is applied to a clean interface superconductor, a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like phase is stabilized. This phase has a U(1)xU(1) symmetry and, in principle, this symmetry allows for flux carrying topological excitations different from Abrikosov vortices (which are the simplest defects associated with S-1 --> S-1 maps). However, in practice, largely due to electromagnetic and other intercomponent interactions, such topological excitations are very rare in superconducting systems. Here, we demonstrate that a realistic microscopic theory for interface superconductors, such as SrTiO3/LaAlO3, predicts an unconventional magnetic response where the flux-carrying objects are skyrmions, characterized by homotopy invariants of S-2 --> S-2 maps. Additionally, we show that this microscopic theory predicts that stable fractional vortices form near the boundary of these superconductors. It also predicts the appearance of type-1.5 superconductivity for some range of parameters. Central to these results is the assumption that the Rashba spin-orbit coupling is much larger than the superconducting gap.

  • 8. Agterberg, Daniel F.
    et al.
    Garaud, Julien
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Checkerboard order in vortex cores from pair-density-wave superconductivity2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 10, article id 104512Article in journal (Refereed)
    Abstract [en]

    We consider competing pair-density-wave (PDW) and d-wave superconducting states in a magnetic field. We show that PDW order appears in the cores of d-wave vortices, driving checkerboard charge-density-wave (CDW) order in the vortex cores, which is consistent with experimental observations. Furthermore, we find an additional CDW order that appears on a ring outside the vortex cores. This CDW order varies with a period that is twice that of the checkerboard CDW and it only appears where both PDW and d-wave order coexist. The observation of this additional CDW order would provide strong evidence for PDW order in the pseudogap phase of the cuprates. We further argue that the CDW seen by nuclear magnetic resonance at high fields is due to a PDW state that emerges when a magnetic field is applied.

  • 9.
    Ahlgren, Björn
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Astrophysical Constraints on Secret Neutrino Interactions2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 10.
    Ahlgren, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Byström, David
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    A Study of Josephson Junction Characteristics.2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This Bachelor thesis has as its aim to investigate Josephson junctions by examining

    their I-V characteristics and to visualize various phenomena associated with Josephson

    junctions. Primarily, everything considered in this thesis uses a semi-classical model

    where quantum eects have been excluded. The thesis focuses on 1D arrays of Josephson

    junctions fed with direct current with the goal to study what occurs when many junctions

    are placed in a row. First a single Josephson junction is simulated and we observe a

    hysteresis in the I-V characteristics that is examined. Secondly a 1-D array is considered

    and the coupled system of dierential equations that follows is solved numerically, and

    from this data the properties of Josephson junctions are deduced. We discovered that this

    array generally has similar properties to a single Josephson junction. We also sought to

    replicate results obtained experimentally in the lab by David Haviland and his co-workers

    at KTH, but by simulations, to see how good our models are. We have produced data

    agreeing partly with the experimental results and we have had no directly contradicting

    outcomes from our simulations. An explicit relation between the number of Josephson

    junctions and the feature of the I-V characteristics was derived and the validity of our

    model was strengthened by the consistency of our results.

  • 11.
    Ahlgren, Björn
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zhou, Shun
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Comment on "Is Dark Matter with Long-Range Interactions a Solution to All Small-Scale Problems of Λ Cold Dark Matter Cosmology?"2013In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 111, no 19, p. 199001-Article in journal (Refereed)
  • 12.
    Ahlström, Marcus
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Path Integral Monte Carlo Simulation of Helium-4 Nanodroplets2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 13.
    Akhmedov, Evgeny
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Duality in left-right symmetric seesaw2007In: Nuclear physics B, Proceedings supplements, ISSN 0920-5632, E-ISSN 1873-3832, Vol. 168, p. 369-371Article in journal (Refereed)
    Abstract [en]

    A reconstruction of the mass matrix of heavy right-handed Majorana neutrinos is performed in the framework of the left-right symmetric type I+II seesaw mechanism. An intriguing pairwise duality relation between different solutions is shown to exist.

  • 14.
    Akhmedov, Evgeny
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Neutrino oscillations: Theory and phenomenology2011In: Nuclear Physics B - Proceedings Supplements, ISSN 0920-5632, Vol. 221, p. 19-25Article in journal (Refereed)
    Abstract [en]

    A brief overview of selected topics in the theory and phenomenology of neutrino oscillations is given. These include: oscillations in vacuum and in matter; phenomenology of 3-flavour neutrino oscillations; CP and T violation in neutrino oscillations in vacuum and in matter; matter effects on ν μ↔ν τ oscillations; parametric resonance in neutrino oscillations inside the earth; oscillations below and above the MSW resonance; unsettled issues in the theory of neutrino oscillations.

  • 15.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Blennow, Mattias
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Hällgren, Tomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Konstandin, Thomas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Stability and leptogenesis in the left-right symmetric seesaw mechanism2007In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 4, p. 022-1-022-25Article in journal (Refereed)
    Abstract [en]

    We analyze the left-right symmetric type I+II seesaw mechanism, where an eight-fold degeneracy among the mass matrices of heavy right-handed neutrinos M-R is known to exist. Using the stability property of the solutions and their ability to lead to successful baryogenesis via leptogenesis as additional criteria, we discriminate among these eight solutions and partially lift their eight-fold degeneracy. In particular, we find that viable leptogenesis is generically possible for four out of the eight solutions.

  • 16.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Frigerio, M.
    Duality in left-right symmetric seesaw2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T127, p. 59-61Article in journal (Refereed)
    Abstract [en]

    We perform a reconstruction of the mass matrix of heavy right-handed Majorana neutrinos in the framework of the left - right symmetric type I + II seesaw mechanism. An intriguing pairwise duality relation between different solutions is shown to exist.

  • 17.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Frigerio, Michele
    Interplay of type I and type II seesaw contributions to neutrino mass2007In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 1, p. 043-Article in journal (Refereed)
    Abstract [en]

    Type I and type II seesaw contributions to the mass matrix of light neutrinos are inherently related if left-right symmetry is realized at high energy scales. We investigate implications of such a relation for the interpretation of neutrino data. We proved recently that the left-right symmetric seesaw equation has eight solutions, related by a duality property, for the mass matrix of right-handed neutrinos M-R. In this paper the eight allowed structures of M-R are reconstructed analytically and analyzed numerically in a bottom-up approach. We study the dependence of right-handed neutrino masses on the mass spectrum of light neutrinos, mixing angle theta(13), leptonic CP violation, scale of left-right symmetry breaking and on the hierarchy in neutrino Yukawa couplings. The structure of the seesaw formula in several specific SO(10) models is explored in the light of the duality. The outcome of leptogenesis may depend crucially on the choice among the allowed structures of M-R and on the level crossing between right-handed neutrino masses.

  • 18.
    Akhmedov, Evgeny Kh
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Neutrino oscillations: Theory and phenomenology2006In: NEUTRINO - Proc. Int. Conf. Neutrino Phys. Astrophys., 2006, p. 16-22Conference paper (Refereed)
    Abstract [en]

    A brief overview of selected topics in the theory and phenomenology of neutrino oscillations is given. These include: oscillations in vacuum and in matter; phenomenology of 3-flavour neutrino oscillations; CP and T violation in neutrino oscillations in vacuum and in matter; matter effects on νμ ↔ ντ oscillations; parametric resonance in neutrino oscillations inside the earth; oscillations below and above the MSW resonance; unsettled issues in the theory of neutrino oscillations.

  • 19.
    Akhmedov, Evgeny
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Maltoni, Michele
    Smirnov, Alexei Yu.
    1-3 leptonic mixing and the neutrino oscillograms of the Earth2007In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 5, p. 077-Article in journal (Refereed)
    Abstract [en]

    We develop a detailed and comprehensive description of neutrino oscillations driven by the 1-3 mixing in the matter of the Earth. The description is valid for the realistic (PREM) Earth density profile in the whole range of nadir angles and for neutrino energies above 1 GeV. It can be applied to oscillations of atmospheric and accelerator neutrinos. The results are presented in the form of neutrino oscillograms of the Earth, i.e. the contours of equal oscillation probabilities in the neutrino energy-nadir angle plane. A detailed physics interpretation of the oscilligrams, which includes the MSW peaks, parametric ridges, local maxima, zeros and saddle points, is given in terms of the amplitude and phase conditions. Precise analytic formulas for the probabilities are obtained. We study the dependence of the oscillation pattern on theta(13) and find, in particular, that the survival probability P-ee < 1/2 appears for sin(2) 2 theta(13) as small as similar to 0.009. We consider the dependence of the oscillation pattern on the matter density profile and comment on the possibility of the oscillation tomography of the Earth.

  • 20. Ali, E. S.
    et al.
    Rajapaksha, H.
    Lundborg, Magnus
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Carr, J. M.
    Petrovsky, N.
    Norovirus drug candidates that inhibit viral capsid attachment to human histo-blood group antigens2016In: Antiviral Research, ISSN 0166-3542, E-ISSN 1872-9096, Vol. 133, p. 14-22Article in journal (Refereed)
    Abstract [en]

    Human noroviruses are the leading causative agents of epidemic and sporadic viral gastroenteritis and childhood diarrhoea worldwide. Human histo-blood group antigens (HBGA) serve as receptors for norovirus capsid protein attachment and play a critical role in infection. This makes HBGA-norovirus binding a promising target for drug development. Recently solved crystal structures of norovirus bound to HBGA have provided a structural basis for identification of potential anti-norovirus drugs and subsequently performed in silico and in vitro drug screens have identified compounds that block norovirus binding and may thereby serve as structural templates for design of therapeutic norovirus inhibitors. This review explores norovirus therapeutic options based on the strategy of blocking norovirus-HBGA binding.

  • 21. Alidoust, Mohammad
    et al.
    Zyuzin, Alexander
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Halterman, Klaus
    Pure odd-frequency superconductivity at the cores of proximity vortices2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 4, article id 045115Article in journal (Refereed)
    Abstract [en]

    After more than a decade, direct observation of the odd frequency triplet pairing state in superconducting hybrid structures remains elusive. We propose an experimentally feasible setup that can unambiguously reveal the zero energy peak due to proximity-induced equal spin superconducting triplet correlations. We theoretically investigate a two-dimensional Josephson junction in the diffusive regime. The nanostructure consists of a normal metal sandwiched between two ferromagnetic layers with spiral magnetization patterns. By applying an external magnetic field perpendicular to the junction plane, vortices nucleate in the normal metal. The calculated energy and spatially resolved density of states, along with the pair potential, reveal that remarkably, only triplet Cooper pairs survive in the vortex cores. These isolated odd frequency triplet correlations result in well defined zero energy peaks in the local density of states that can be identified through tunneling spectroscopy experiments. Moreover, the diffusive regime considered here rules out the possibility of Andreev bound states in the vortex core as contributors to the zero energy peaks.

  • 22.
    Allard, Filip
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Blomqvist, David
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Boomeron- and Trappon Solitons InvestigatedAnalytically and Numerically2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report presents an analysis of the phenomena of boomeron- and trappon solitons

    both analytically and numerically. These solitons are investigated in the (1+1) dimension,

    i.e. one spatial dimension plus the temporal dimension. The investigation regards the

    Boomeron equation (BE) and the non-linear Schrödinger equation (NLSE). Additional

    equations giving rise to these phenomena are also presented. A special focus of the

    investigation is the relation between the changing velocity and the polarization for the BE

    and the NLSE. For the NLSE, this is enabled through an interpretation of the components

    for the single-soliton solution.

    The BE is solved analytically through the inverse scattering transform. The analytical

    solutions for the BE and NLSE are compared with numerically obtained single-soliton

    solutions for the two equations respectively. The numerical solutions are conducted using

    a finite difference method (FDM) based on central difference.

  • 23.
    Alp, Dennis
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Modée, Samuel
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Dark Matter: Particle Evolution through Freeze-out2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report focuses on the evolution of dark matter particles in a simplied, homogeneous

    and isotropic model of the Universe. The purpose is to analyze theoretical predictions and

    recent experimental measurements to be able to draw conclusions about the properties

    of the dark matter particles. The inexperienced reader is introduced to the subject and

    thorough derivations of the formulas relevant to the analysis are made. To analyze the

    evolution of dark matter, the Boltzmann equation is applied to a freeze-out model. Both

    analytical and numerical approaches will be taken and discrepancies between those are

    investigated. Qualitative eects of the particle cross section and mass are studied and

    constraints on the parameters are set using experimental data. Finally, assumptions are

    discussed and suggestions for further research are made.

  • 24.
    Andersson, Andreas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Phase fluctuation phenomena in superconductors2012Doctoral thesis, comprehensive summary (Other academic)
  • 25.
    Andersson, Andreas
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Simulations of thermoelectric transport in granularsuperconductors2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents results from numerical simulations of the Nernst effect dueto phase fluctuations in models of two-dimensional granular superconductors. Inaddition other transport properties, such as thermal conductivity and electrical re-sistivity are calculated. The models are based on a phase only description withLangevin or resistively and capacitively shunted Josephson junction (RCSJ) dy-namics, generalized to be valid for any type of two-dimensional lattice structure.All transport coefficients are evaluated from equilibrium correlation functions usingKubo formulas.

    In Paper I, anomalous sign reversals of the Nernst signal eN , corresponding tovortex motion from colder to hotter regions, are observed. These are attributedto geometric frustration effects close to magnetic fields commensurate with theunderlying lattice structure. The effect is seen also in systems with moderategeometric disorder, and should thus be possible to observe in real two-dimensionalgranular superconductors or Josephson junction arrays.

    Paper II presents two different derivations of an expression for the heat current inLangevin and RCSJ dynamics. The resulting expression is through our simulationsseen to obey the required Onsager relation, as well as giving consistent resultswhen calculating κ and eN via Kubo formulas and through the responses to anapplied temperature gradient. In zero magnetic field and at low-temperatures, thecontribution to the thermal conductivity κ in RCSJ dynamics is calculated usinga spin-wave approximation, and is shown to be independent of temperature anddiverge logarithmically with system size. At higher temperatures, κ shows a non-monotonic temperature dependence. In zero magnetic field κ has a anomalouslogarithmic size dependence also in this regime. The off-diagonal component ofthe thermoelectric tensor αxy is calculated and displays the very same ∼1/T dependence at low temperatures predicted from calculations based on Gaussiansuperconducting fluctuations.

  • 26.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Anomalous Nernst effect and heat transport by vortex vacancies in granular superconductors2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 6, p. 060508-1-060508-4Article in journal (Refereed)
    Abstract [en]

    We study the Nernst effect due to vortex motion in two-dimensional granular superconductors using simulations with Langevin or resistively shunted Josephson-junction dynamics. In particular, we show that the geometric frustration of both regular and irregular granular materials can lead to thermally driven transport of vortices from colder to hotter regions, resulting in a sign reversal of the Nernst signal. We discuss the underlying mechanisms of this anomalous behavior in terms of heat transport by mobile vacancies in an otherwise pinned vortex lattice.

  • 27.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Influence of vortices and phase fluctuations on thermoelectric transport properties of superconductors in a magnetic field2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 17, p. 174502-Article in journal (Refereed)
    Abstract [en]

    We study heat transport and thermoelectric effects in two-dimensional superconductors in a magnetic field. These are modeled as granular Josephson-junction arrays, forming either regular or random lattices. We employ two different models for the dynamics: relaxational model-A dynamics or resistively and capacitively shunted Josephson junction dynamics. We derive expressions for the heat current in these models, which are then used in numerical simulations to calculate the heat conductivity and Nernst coefficient for different temperatures and magnetic fields. At low temperatures and zero magnetic field the heat conductivity in the RCSJ model is calculated analytically from a spin wave approximation, and is seen to have an anomalous logarithmic dependence on the system size, and also to diverge in the completely overdamped limit C -> 0. From our simulations we find at low magnetic fields that the Nernst signal displays a characteristic "tilted hill" profile similar to experiments and a nonmonotonic temperature dependence of the heat conductivity. We also investigate the effects of granularity and randomness, which become important for higher magnetic fields. In this regime geometric frustration strongly influences the results in both regular and random systems and leads to highly nontrivial magnetic field dependencies of the studied transport coefficients.

  • 28.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Modeling and simulations of quantum phase slips in ultrathin superconducting wiresManuscript (preprint) (Other academic)
  • 29.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Modeling and simulations of quantum phase slips in ultrathin superconducting wires2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 13, article id 134504Article in journal (Refereed)
    Abstract [en]

    We study quantum phase slips (QPS) in ultrathin superconducting wires. Starting from an effective one-dimensional microscopic model, which includes electromagnetic fluctuations, we map the problem to a (1+1)-dimensional gas of interacting instantons. We introduce a method to calculate the tunneling amplitude of quantum phase slips directly from Monte Carlo simulations. This allows us to go beyond the dilute instanton gas approximation and study the problem without any limitations of the density of QPS. We find that the tunneling amplitude shows a characteristic scaling behavior near the superconductor-insulator transition. We also calculate the voltage-charge relation of the insulating state, which is the dual of the Josephson current-phase relation in ordinary superconducting weak links. This evolves from a sinusoidal form in the regime of dilute QPS to more exotic shapes for higher QPS densities, where interactions are important.

  • 30.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Scaling, Finite Size Effects, and Crossovers of the Resistivity and Current-Voltage Characteristics in Two-Dimensional SuperconductorsManuscript (preprint) (Other academic)
    Abstract [en]

    We revisit the scaling properties of the resistivity and the current-voltage characteristics at and below the Berezinskii-Kosterlitz-Thouless transition, both in zero and nonzero magnetic field. The scaling properties are derived by integrating the renormalization group flow equations up to a scale where they can be reliably matched to simple analytic expressions. The vortex fugacity turns out to be dangerously irrelevant for these quantities below $T_c$, thereby altering the scaling behavior. We derive the possible crossover effects as the current, magnetic field or system size is varied, and find a strong multiplicative logarithmic correction near $T_c$, all which is necessary to account for when interpreting experiments and simulation data. Our analysis clarifies a longstanding discrepancy between the finite size dependence found in many simulations and the current-voltage characteristics of experiments. We further show that the logarithmic correction can be avoided by approaching the transition in a magnetic field, thereby simplifying the scaling analysis. We confirm our results by large scale numerical simulations, and calculate the dynamic critical exponent $z$, for relaxational Langevin dynamics and for resistively and capacitively shunted Josephson junction dynamics.

  • 31.
    Andersson, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Lidmar, Jack
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Scaling, finite size effects, and crossovers of the resistivity and current-voltage characteristics in two-dimensional superconductors2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 22, p. 224506-Article in journal (Refereed)
    Abstract [en]

    We revisit the scaling properties of the resistivity and the current-voltage characteristics at and below the Berezinskii-Kosterlitz-Thouless transition, both in zero and nonzero magnetic fields. The scaling properties are derived by integrating the renormalization group flow equations up to a scale where they can be reliably matched to simple analytic expressions. The vortex fugacity turns out to be dangerously irrelevant for these quantities below T-c, thereby altering the scaling behavior. We derive the possible crossover effects as the current, magnetic field, or system size is varied, and find a strong multiplicative logarithmic correction near T-c, all of which is necessary to account for when interpreting experiments and simulation data. Our analysis clarifies a longstanding discrepancy between the finite size dependence found in many simulations and the current-voltage characteristics of experiments. We further show that the logarithmic correction can be avoided by approaching the transition in a magnetic field, thereby simplifying the scaling analysis. We confirm our results by large-scale numerical simulations, and calculate the dynamic critical exponent z, for relaxational Langevin dynamics and for resistively and capacitively shunted Josephson junction dynamics.

  • 32.
    Andersson, Magnus
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Espinosa-Arronte, Beatriz
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    van der Beek, C. J.
    Nikolaou, M.
    Lidmar, J.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Wallin, M.
    A vortex solid-to-liquid transition with fully anisotropic scaling2009In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 150, no 5Article in journal (Refereed)
    Abstract [en]

    The vortex solid-to-liquid transition has been studied in heavy ion irradiated untwinned single crystals of YBa2Cu3O7-delta with an inclined applied magnetic field. For magnetic fields tilted at angles about 45 degrees away from the columnar defects, we find that the electric resistivity in the vortex liquid regime approaches zero with power laws in the reduced temperature T - T-c that have different exponents in all three spatial directions. Since the symmetry in the problem has been broken in two non-collinear directions by i) the direction of the columnar defects and ii) the direction of the applied magnetic field, our findings give evidence for a new type of critical behavior with fully anisotropic critical exponents. A possible view of the vortex topology for the transition is also suggested.

  • 33.
    Andersson, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Mattle, Daniel
    Sitsel, Oleg
    Nielsen, Anna Marie
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    White, Stephen H.
    Nissen, Poul
    Gourdon, Pontus
    Transport Pathway in Cu+ P-Type ATPases2014In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 106, no 2, p. 427A-427AArticle in journal (Other academic)
  • 34.
    Andresen, Juan Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics. ETH, Switzerland.
    Katzgraber, Helmut G.
    Oganesyan, Vadim
    Schechter, Moshe
    Existence of a Thermodynamic Spin-Glass Phase in the Zero-Concentration Limit of Anisotropic Dipolar Systems2014In: Physical Review X, ISSN 2160-3308, E-ISSN 2160-3308, Vol. 4, no 4, p. 041016-Article in journal (Refereed)
    Abstract [en]

    The nature of ordering in dilute dipolar interacting systems dates back to the work of Debye and is one of the most basic, oldest and as-of-yet unsettled problems in magnetism. While spin-glass order is readily observed in several RKKY-interacting systems, dipolar spin glasses are the subject of controversy and ongoing scrutiny, e.g., in LiHoxY1-xF4, a rare-earth randomly diluted uniaxial (Ising) dipolar system. In particular, it is unclear if the spin-glass phase in these paradigmatic materials persists in the limit of zero concentration or not. We study an effective model of LiHoxY1-xF4 using large-scale Monte Carlo simulations that combine parallel tempering with a special cluster algorithm tailored to overcome the numerical difficulties that occur at extreme dilutions. We find a paramagnetic to spin-glass phase transition for all Ho+ ion concentrations down to the smallest concentration numerically accessible, 0.1%, and including Ho+ ion concentrations that coincide with those studied experimentally up to 16.7%. Our results suggest that randomly diluted dipolar Ising systems have a spin-glass phase in the limit of vanishing dipole concentration, with a critical temperature vanishing linearly with concentration. The agreement of our results with mean-field theory testifies to the irrelevance of fluctuations in interactions strengths, albeit being strong at small concentrations, to the nature of the low-temperature phase and the functional form of the critical temperature of dilute anisotropic dipolar systems. Deviations from linearity in experimental results at the lowest concentrations are discussed.

  • 35.
    Andresen, Juan Carlos
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory. Theoretische Physik, ETH Zurich, Zurich, Switzerland.
    Pramudya, Yohanes
    Katzgraber, Helmut G.
    Thomas, Creighton K.
    Zimanyi, Gergely T.
    Dobrosavljevic, V.
    Charge avalanches and depinning in the Coulomb glass: The role of long-range interactions2016In: Physical Review B, ISSN 2469-9950, Vol. 93, no 9, article id 094429Article in journal (Refereed)
    Abstract [en]

    We explore the stability of far-from-equilibrium metastable states of a three-dimensional Coulomb glass at zero temperature by studying charge avalanches triggered by a slowly varying external electric field. Surprisingly, we identify a sharply defined dynamical ("depinning") phase transition from stationary to nonstationary charge displacement at a critical value of the external electric field. Using particle-conserving dynamics, scale-free system-spanning avalanches are observed only at the critical field. We show that the qualitative features of this depinning transition are completely different for an equivalent short-range model, highlighting the key importance of long-range interactions for nonequilibrium dynamics of Coulomb glasses.

  • 36. Antusch, Stefan
    et al.
    King, Stephen F.
    Malinský, Michal
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Perturbative estimates of lepton mixing angles in unified models2009In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 820, no 1-2, p. 32-46Article in journal (Refereed)
    Abstract [en]

    Many unified models predict two large neutrino mixing angles, with the charged lepton mixing angles being small and quark-like, and the neutrino masses being hierarchical. Assuming this, we present simple approximate analytic formulae giving the lepton mixing angles in terms of the underlying high energy neutrino mixing angles together with small perturbations due to both charged lepton corrections and renormalisation group (RG) effects, including also the effects of third family canonical normalization (CN). We apply the perturbative formulae to the ubiquitous case of tri-bimaximal neutrino mixing at the unification scale, in order to predict the theoretical corrections to mixing angle predictions and sum rule relations, and give a general discussion of all limiting cases. We also discuss the implications for the sum rule relations of the measurement of a non-zero reactor angle, as hinted at by recent experimental measurements.

  • 37. Antusch, Stefan
    et al.
    King, Stephen F.
    Malinský, Michal
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Spinrath, Martin
    Quark mixing sum rules and the right unitarity triangle2010In: Physical Review D - Particles, Fields, Gravitation and Cosmology, ISSN 1550-7998, Vol. 81, no 3, p. 033008-Article in journal (Refereed)
    Abstract [en]

    In analogy with the recently proposed lepton mixing sum rules, we derive quark mixing sum rules for the case of hierarchical quark mass matrices with 1-3 texture zeros, in which the separate up and down-type 1-3 mixing angles are approximately zero, and V-ub is generated from V-cb as a result of 1-2 up-type quark mixing. Using the sum rules, we discuss the phenomenological viability of such textures, including up to four texture zeros, and show how the right-angled unitarity triangle, i.e., alpha approximate to 90 degrees, can be accounted for by a remarkably simple scheme involving real mass matrices apart from a single element being purely imaginary. In the framework of grand unified theories, we show how the quark and lepton mixing sum rules may combine to yield an accurate prediction for the reactor angle.

  • 38.
    Apostolov, Rossen
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Axner, Lilit
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Agren, Hans
    Ayugade, Eduard
    Duta, Mihai
    Gelpi, Jose Luis
    Gimenez, Judit
    Goni, Ramon
    Hess, Berk
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Jamitzky, Ferdinand
    Kranzmuller, Dieter
    Labarta, Jesus
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Lindahl, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical & Computational Biophysics.
    Orozco, Modesto
    Peterson, Magnus
    Satzger, Helmut
    Trefethen, Anne
    Scalable Software Services for Life Science2011In: Proceedings of 9th HealthGrid conference, 2011Conference paper (Refereed)
    Abstract [en]

    Life Science is developing into one of the largest e- Infrastructure users in Europe, in part due to the ever-growing amount of biological data. Modern drug design typically includes both sequence bioinformatics, in silico virtual screening, and free energy calculations, e.g. of drug binding. This development will accelerate tremendously, and puts high demands on simulation software and support services. e-Infrastructure projects such as PRACE/DEISA have made important advances on hardware and scalability, but have largely been focused on theoretical scalability for large systems, while typical life science applications rather concern small-to-medium size molecules. Here, we propose to address this with by implementing new techniques for efficient small-system parallelization combined with throughput and ensemble computing to enable the life science community to exploit the largest next-generation e-Infrastructures. We will also build a new cross-disciplinary Competence Network for all of life science, to position Europe as the world-leading community for development and maintenance of this software e-Infrastructure. Specifically, we will (1) develop new hierarchical parallelization approaches explicitly based on ensemble and high-throughput computing for new multi-core and streaming/GPU architectures, and establish open software standards for data storage and exchange, (2) implement, document, and maintain such techniques in pilot European open-source codes such as the widely used GROMACS & DALTON, a new application for ensemble simulation (DISCRETE), and large-scale bioinformatics protein annotation, (3) create a Competence Centre for scalable life science software to strengthen Europe as a major software provider and to enable the community to exploit e-Infrastructures to their full extent. This Competence Network will provide training and support infrastructure, and establish a long-term framework for maintenance and optimization of life science codes.

  • 39.
    Ardelius, John
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Aurell, Erik
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Behavior of heuristics on large and hard satisfiability problems2006In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 74, no 3, p. 037702-Article in journal (Refereed)
    Abstract [en]

     We study the behavior of a heuristic for solving random satisfiability problems by stochastic local search near the satisfiability threshold. The heuristic for average satisfiability (ASAT), is similar to the Focused Metropolis Search heuristic, and shares the property of being focused, i.e., only variables in unsatisfied clauses are updated in each step. It is significantly simpler than the benchmark WALKSAT heuristic. We show that ASAT solves instances as large as N=10(6) in linear time, on average, up to a ratio of 4.21 clauses per variable in random three-satisfiability. For K higher than 3, ASAT appears to solve instances of K-satisfiability up to the Montanari-Ricci-Tersenghi-Parisi full replica symmetry breaking (FSRB) threshold denoted alpha(s)(K) in linear time.

  • 40.
    Armiento, Rickard
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    The many-electron energy in density functional theory: from exchange-correlation functional design to applied electronic structure calculations2005Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The prediction of properties of materials and chemical systems is a key component in theoretical and technical advances throughout physics, chemistry, and biology. The properties of a matter system are closely related to the configuration of its electrons. Computer programs based on density functional theory (DFT) can calculate the configuration of the electrons very accurately. In DFT all the electronic energy present in quantum mechanics is handled exactly, except for one minor part, the exchange-correlation (XC) energy. The thesis discusses existing approximations of the XC energy and presents a new method for designing XC functionals---the subsystem functional scheme. Numerous theoretical results related to functional development in general are presented. An XC functional is created entirely without the use of empirical data (i.e., from so called first-principles). The functional has been applied to calculations of lattice constants, bulk moduli, and vacancy formation energies of aluminum, platinum, and silicon. The work is expected to be generally applicable within the field of computational density functional theory.

  • 41. Asker, C.
    et al.
    Belonoshko, Anatoly B.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Condensed Matter Theory.
    Mikhaylushkin, A. S.
    Abrikosov, I. A.
    First-principles solution to the problem of Mo lattice stability2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 22Article in journal (Refereed)
    Abstract [en]

    The energy differences between the ground state body-centered structure and closed-packed face-centered structure for transition metals in the middle of the series show unusually large disagreements when they are obtained by the thermochemical approach based on the analysis of experimental data or by first-principles electronic structure calculations. Considering a typical example, the lattice stability of Mo, we present a solution to this long-standing problem. We carry out ab initio molecular dynamics simulations for the two phases at high temperature and show that the configurational energy difference approaches the value derived by means of the thermochemical approach. The main contribution to the effect comes from the modification of the canonical band structure due to anharmonic thermal motion at high temperature.

  • 42.
    Atai, Farrokh
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    A kernel function approach to exact solutions of Calogero-Moser-Sutherland type models2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This Doctoral thesis gives an introduction to the concept of kernel functionsand their signicance in the theory of special functions. Of particularinterest is the use of kernel function methods for constructing exact solutionsof Schrodinger type equations, in one spatial dimension, with interactions governedby elliptic functions. The method is applicable to a large class of exactlysolvable systems of Calogero-Moser-Sutherland type, as well as integrable generalizationsthereof. It is known that the Schrodinger operators with ellipticpotentials have special limiting cases with exact eigenfunctions given by orthogonalpolynomials. These special cases are discussed in greater detail inorder to explain the kernel function methods with particular focus on the Jacobipolynomials and Jack polynomials.

  • 43.
    Atai, Farrokh
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Anyons in (1 + 1) dimensions and the deformed Calogero-Sutherland model2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis deals with a conformal field theoretical treatment of abelian anyons in (1 + 1)-dimensions and their relation to the integrable Calogero-Sutherland models.

    We generalize previous work relating anyons to the Calogero-Sutherland model by showing that the correlation function of the anyon field operators corresponds to the eigenfunctions of the deformed Calogero-Sutherland model. Our results suggest a physical application of the deformed Calogero-Sutherland model in the context of the fractional quantum Hall effect (FQHE).

    A key aspect for this work is the introduction of the dual anyon field operators, which obey a natural generalization of the canonical anti-commutation relation.

  • 44.
    Atai, Farrokh
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
    Integral representation of solution to the non-stationary Lamé equationManuscript (preprint) (Other academic)
    Abstract [en]

    We consider methods for constructing explicit solutions of the non-stationary Lame equation,which is a generalization of the classical Lame equation, that has appeared in works on integrablemodels, conformal eld theory, high energy physics and representation theory. We also present ageneral method for constructing integral representations of solutions to the non-stationary Lameequation by a recursive scheme. Explicit integral representations, for special values of the modelparameters, are also presented. Our approach is based on kernel function methods which can benaturally generalized to the non-stationary Heun equation.

  • 45.
    Atai, Farrokh
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
    Hallnäs, Martin
    Langmann, Edwin
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
    Source Identities and Kernel Functions for Deformed (Quantum) Ruijsenaars Models2014In: Letters in Mathematical Physics, ISSN 0377-9017, E-ISSN 1573-0530, Vol. 104, no 7, p. 811-835Article in journal (Refereed)
    Abstract [en]

    We consider the relativistic generalization of the quantum A (N-1) Calogero-Sutherland models due to Ruijsenaars, comprising the rational, hyperbolic, trigonometric and elliptic cases. For each of these cases, we find an exact common eigenfunction for a generalization of Ruijsenaars analytic difference operators that gives, as special cases, many different kernel functions; in particular, we find kernel functions for Chalykh-Feigin-Veselov-Sergeev-type deformations of such difference operators which generalize known kernel functions for the Ruijsenaars models. We also discuss possible applications of our results.

  • 46.
    Atai, Farrokh
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Hoppe, Jens
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Hynek, Mariusz
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Langmann, Edwin
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Variational orthogonalizationManuscript (preprint) (Other academic)
    Abstract [en]

    We introduce variational methods for finding approximate eigenfunctions and eigenvalues of quantum Hamiltonians by constructing a set of orthogonal wave functions which approximately solve the eigenvalue equation.

  • 47.
    Atai, Farrokh
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
    Langmann, Edwin
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
    Deformed Calogero-Sutherland model and fractional Quantum Hall effectManuscript (preprint) (Other academic)
    Abstract [en]

    The deformed Calogero-Sutherland (CS) model is a quantum integrable systemwith arbitrary numbers of two types of particles and reducing to the standard CSmodel in special cases. We show that a known collective field description of theCS model, which is based on conformal field theory (CFT), is actually a collectivefield description of the deformed CS model. This provides a natural application ofthe deformed CS model in Wen’s effective field theory of the fractional quantumHall effect (FQHE), with the two kinds of particles corresponding to electrons andquasi-hole excitations. In particular, we use known mathematical results aboutsuper Jack polynomials to obtain simple explicit formulas for the orthonormal CFTbasis proposed by van Elburg and Schoutens in the context of the FQHE.

  • 48.
    Atai, Farrokh
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Langmann, Edwin
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Deformed Calogero-Sutherland model and fractional quantum Hall effect2017In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 58, no 1, article id 011902Article in journal (Refereed)
    Abstract [en]

    The deformed Calogero-Sutherland (CS) model is a quantum integrable system with arbitrary numbers of two types of particles and reducing to the standard CS model in special cases. We show that a known collective field description of the CS model, which is based on conformal field theory (CFT), is actually a collective field description of the deformed CS model. This provides a natural application of the deformed CS model in Wen's effective field theory of the fractional quantum Hall effect (FQHE), with the two kinds of particles corresponding to electrons and quasi-hole excitations. In particular, we use known mathematical results about super-Jack polynomials to obtain simple explicit formulas for the orthonormal CFT basis proposed by van Elburg and Schoutens in the context of the FQHE.

  • 49.
    Atai, Farrokh
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
    Langmann, Edwin
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Mathematical Physics.
    Series solutions of the non-stationary Heun equationManuscript (preprint) (Other academic)
    Abstract [en]

    We consider the non-stationary Heun equation, also known as quantum PainlevéVI, which has appeared in dierent works on quantum integrable models and conformaleld theory. We use a generalized kernel function identity to transform the problemto solve this equation into a dierential-dierence equation which, as we show, canbe solved by ecient recursive algorithms. We thus obtain series representations ofsolutions which provide elliptic generalizations of the Jacobi polynomials. These seriesreproduces, in a limiting case, a perturbative solution of the Heun equation due toTakemura, but our method is dierent in that we expand in non-conventional basisfunctions that allow us to obtain explicit formulas to all orders;

  • 50.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Statistical Physics.
    Non-Meissner electrodynamics and knotted solitons in two-component superconductors2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 10Article in journal (Refereed)
    Abstract [en]

    I consider electrodynamics and the problem of knotted solitons in two-component superconductors. Possible existence of knotted solitons in multicomponent superconductors was predicted several years ago. However, their basic properties and stability in these systems remain an outstandingly difficult question both for analytical and numerical treatment. Here I propose a special perturbative approach to treat self-consistently all the degrees of freedom in the problem. I show that there exists a length scale for a Hopfion texture where the electrodynamics of a two-component superconductor is dominated by a self-induced Faddeev term, which is in stark contrast to the Meissner electrodynamics of single-component systems. I also show that at certain short length scales knotted solitons in the two-component Ginzburg-Landau model are not described by a Faddeev-Skyrme-type model and are unstable. However, these solitons can be stable at some intermediate length scales. I argue that configurations with high topological charge may be more stable in these systems than low-charge configurations. In the second part of the paper I discuss qualitatively different physics of the stability of knotted solitons in a more general Ginzburg-Landau model and point out the physically relevant terms which enhance or suppress the stability of knotted solitons. With this argument it is demonstrated that Ginzburg-Landau models possess stable knotted solitons.

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