Svistunov, Boris
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Professor, Physics Department
Last Name
Svistunov
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Boris
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Physics
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Theoretical Condensed Matter Physics
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Publication Open Access Critical Temperature Curve in BEC-BCS Crossover(2008-01) Burovski, E; Kozik, E; Prokof'ev, N; Svistunov, B; Troyer, MThe strongly correlated regime of the crossover from Bardeen-Cooper-Schrieffer pairing to Bose-Einstein condensation can be realized by diluting a system of two-component fermions with a short-range attractive interaction. We investigate this system via a novel continuous-space-time diagrammatic determinant Monte Carlo method and determine the universal curve Tc/εF for the transition temperature between the normal and the superfluid states as a function of the scattering length with the maximum on the Bose-Einstein condensation side. At unitarity, we confirm that Tc/εF=0.152(7).Publication Open Access Comment on “Hausdorff Dimension of Critical Fluctuations in Abelian Gauge Theories”(2006-01) Prokof'ev, N; Svistunov, BA Comment on the Letter by J. Hove, S. Mo, and A. Sudbø Phys. Rev. Lett. 85, 2368 (2000). The authors of the Letter offer a Reply.Publication Open Access Comment on “Phase Diagram of a Disordered Boson Hubbard Model in Two Dimensions”(2003-01) Prokof’ev, N; Svistunov, BIn a recent Letter [1] (see also [2]) the authors presented numerical evidence supporting an idea of a direct transition between the superfluid (SF) and Mott insulating (MI) phases in the disordered Bosonic system, and even studied non-trivial properties of the multicritical line where SF, MI and the Bose Glass (BG) phases meet. The results were obtained from Monte Carlo simulations of the (2+1)-dimensional classical loop-current model [3] with the lattice action S = 1 2K Þ E ~ J=0 XrƒÑ ~ J2(r, ƒÑ) . 2(ƒÊ + v(r)) ~ JƒÑ (r, ƒÑ) . (1) where r, ƒÑ are spatial and imaginary time coordinates, and ~ J(r, ƒÑ) are integer current vectors with zero divergence. The spatial disorder potential v(r) is uniformly distributed on the interval (.,).Publication Open Access Weakly Interacting Bose Gas in the Vicinity of the Critical Point(2004-01) Prokof'ev, Nikolai; Ruebenacker, O; Svistunov, BorisWe consider a three-dimensional weakly interacting Bose gas in the fluctuation region (and its vicinity) of the normal-superfluid phase transition point. We establish relations between basic thermodynamic functions: density, n(T, ì), superfluid density ns(T, ì), and condensate density, ncnd(T, ì). Being universal for all weakly interacting |ø|4 systems, these relations are obtained from Monte Carlo simulations of the classical |ø|4 model on a lattice. Comparing with the mean-field results yields a quantitative estimate of the fluctuation region size. Away from the fluctuation region, on the superfluid side, all the data perfectly agree with the predictions of the quasicondensate mean field theory.—This demonstrates that the only effect of the leading above-the-mean-field corrections in the condensate based treatments is to replace the condensate density with the quasicondensate one in all local thermodynamic relations. Surprisingly, we find that a significant fraction of the density profile of a loosely trapped atomic gas might correspond to the fluctuation region.Publication Open Access Local Stress and Superfluid Properties of Solid 4He(2008-01) Pollet, L; Boninsegni, M; Kuklov, A; Prokof'ev, Nikolai; Svistunov, Boris; Troyer, MWe provide a semiquantitative tool, derived from first-principles simulations, for answering the question of whether certain types of defects in solid 4He support mass superflow. Although ideal crystals of 4He are not supersolid, the gap for vacancy creation closes when applying a moderate stress. While a homogeneous system becomes unstable at this point, the stressed core of crystalline defects (dislocations and grain boundaries) can turn superfluid.Publication Open Access Weak First-Order Superfluid-Solid Quantum Phase Transitions(2004-01) Kuklov, A; Prokof'ev, Nikolai; Svistunov, BorisWe study superfluid-solid zero-temperature transitions in two-dimensional lattice boson-spin models using worm-algorithm Monte Carlo simulations. We observe that such transitions are typically first order with the exception of special high-symmetry points which require fine-tuning in the Hamiltonian parameter space. We present evidence that the superfluid-checkerboard solid and superfluid–valence-bond solid transitions at half-integer filling factor are extremely weak first-order transitions and in small systems can be confused with continuous or high-symmetry points.Publication Open Access Worm Algorithms for Classical Statistical Models(2001-01) Prokof'ev, Nikolai; Svistunov, BorisWe show that high-temperature expansions provide a basis for the novel approach to efficient Monte Carlo simulations. “Worm” algorithms utilize the idea of updating closed-path configurations (produced by high-temperature expansions) through the motion of end points of a disconnected path. An amazing result is that local, Metropolis-type schemes using this approach appear to have dynamical critical exponents close to zero (i.e., their efficiency is comparable to the best cluster methods) as proved by finite-size scaling of the autocorrelation time for various universality classes.Publication Open Access Worm Algorithm for Problems of Quantum and Classical Statistics(2010-01) Prokof'ev, Nikolai; Svistunov, BorisThis is a chapter of the multi-author book “Understanding Quantum Phase Transitions,” edited by Lincoln Carr and published by Taylor & Francis. In this chapter, we give a general introduction to the worm algorithm and present important results highlighting the power of the approach.Publication Open Access On-site number statistics of ultracold lattice bosons(2007-01) Capogrosso-Sansone, B; Kozik, E; Prokof'ev, Nikolai; Svistunov, BorisWe study on-site occupation number fluctuations in a system of interacting bosons in an optical lattice. The ground-state distribution is obtained analytically in the limiting cases of strong and weak interaction, and by means of exact Monte Carlo simulations in the strongly correlated regime. As the interaction is increased, the distribution evolves from Poissonian in the noninteracting gas to a sharply peaked distribution in the Mott-insulator (MI) regime. In the special case of large occupation numbers, we demonstrate analytically and check numerically that there exists a wide interval of interaction strength, in which the on-site number fluctuations remain Gaussian and are gradually squeezed until they are of order unity near the superfluid (SF)-MI transition. Recently, the on-site number statistics were studied experimentally in a wide range of lattice potential depths [Phys. Rev. Lett. 96, 090401 (2006)]. In our simulations, we are able to directly reproduce experimental conditions using temperature as the only free parameter. Pronounced temperature dependence suggests that measurements of on-site atom number fluctuations can be employed as a reliable method of thermometry in both SF and MI regimes.Publication Open Access Superfluid-Insulator Transition in a Commensurate One-Dimensional Bosonic System with Off-Diagonal Disorder(2005-01) Balabanyan, K; Prokof'ev, Nikolai; Svistunov, BorisWe study the nature of the superfluid-insulator quantum phase transition in a one-dimensional system of lattice bosons with off-diagonal disorder in the limit of a large integer filling factor. Monte Carlo simulations of two strongly disordered models show that the universality class of the transition in question is the same as that of the superfluid-Mott-insulator transition in a pure system. This result can be explained by disorder self-averaging in the superfluid phase and the applicability of the standard quantum hydrodynamic action. We also formulate the necessary conditions which should be satisfied by the stong-randomness universality class, if one exists.