Statistical Mechanics
Signature of Dynamical Heterogeneity in Spatial Correlations of Particle Displacement and its Temporal Evolution in Supercooled Liquids (1906.07699v1)
Indrajit Tah, Smarajit Karmakar
2019-06-18
The existence of heterogeneity in the dynamics of supercooled liquids is believed to be one of the hallmarks of the glass transition. Intense research has been carried out in the past to understand the origin of this heterogeneity in dynamics and a possible length scale associated with it. We have done extensive molecular dynamics simulations of few model glass-forming liquids in three dimensions to understand the temporal evolution of the dynamic heterogeneity and the heterogeneity length scale. We find that although the strength of the dynamic heterogeneity is maximum at a timescale close to characteristic
-relaxation time of the system, dynamic heterogeneity itself is well-developed at timescale as short as
-relaxation time and survives up to a timescale as long as few tens of
Maxwell's demons with finite size and response time (1903.05724v3)
Nathaniel Rupprecht, Dervis Vural
2019-03-13
Nearly all theoretical analyses of the Maxwell's demon focus on its energetic and entropic costs of operation. Here, we focus on its rate of operation. In our model, a demon's rate limitation stems from its finite response time and gate area. We determine the rate limits of mass and energy transfer, as well as entropic reduction for four such demons: Those that select particles according to (1) direction, (2) energy, (3) number and (4) entropy. Lastly, we determine the optimal gate size for a demon with \added{small,} finite response time, \added{and compare our predictions with molecular dynamics simulations with both ideal and non-ideal gasses. Lastly, we study the conditions under which the demons are able to move both energy and particles in the chosen direction when attempting to only move one.
Quantum vs. classical information: operator negativity as a probe of scrambling (1906.07639v1)
Jonah Kudler-Flam, Masahiro Nozaki, Shinsei Ryu, Mao Tian Tan
2019-06-18
We consider the logarithmic negativity and related quantities of time evolution operators. We study free fermion, compact boson, and holographic conformal field theories (CFTs) as well as numerical simulations of random unitary circuits and integrable and chaotic spin chains. The holographic behavior strongly deviates from known non-holographic CFT results and displays clear signatures of maximal scrambling. Intriguingly, the random unitary circuits display nearly identical behavior to the holographic channels. Generically, we find the "line-tension picture" to effectively capture the entanglement dynamics for ergodic systems and the "quasi-particle picture" for integrable systems. With this motivation, we propose an effective line-tension that captures the dynamics of the logarithmic negativity in ergodic systems in the spacetime scaling limit. We compare the negativity and mutual information leading us to find distinct dynamics of quantum and classical information. The "spurious entanglement" we observe may have implications on the "simulatability" of quantum systems on classical computers. Finally, we elucidate the connection between the operation of partially transposing a density matrix in conformal field theory and the entanglement wedge cross section in Anti-de Sitter space using geodesic Witten diagrams.
Two Microspheres in an External Flow: a Dance of Cause and Effect (1906.07621v1)
Golnaz Najafi Gol-Vandani, Simone Di Leo, Jurij Kotar, Pietro Cicuta, Seyyed Nader Rasuli
2019-06-18
In low Reynolds number swimming and pumping, differently to everyday experience, a net motion (or flow) can be achieved only if the constructing parts of the swimmer (or pump) follow a non-trivial pattern of motion, in order to break time reciprocity. The case of a driven fan, which spins to create a flow of air, but conversely rotates when turned off and subjected to a strong external flow, is a familiar example of reciprocal connection between physical cause and effect. We explore here in a well controlled low Reynolds number system whether such an exchange of the cause and effect also holds in the low Reynolds number regime. As a case study we investigate the motion of two microspheres which interact hydrodynamically through their surrounding fluid. Each sphere is constrained in a fixed optical trap potential, allowing local fluctuations around an equilibrium position. An external flow is shown to induce non-trivial coupled motion. We find a signature of reciprocity: the nonequilibrium sphere fluctuations mimic the symmetry of the motions that one would impose in order for them to produce a constant flow.
Conformally invariant boundary conditions in the antiferromagnetic Potts model and the 
sigma model (1906.07565v1)
Niall F. Robertson, Jesper Lykke Jacobsen, Hubert Saleur
2019-06-18
We initiate a study of the boundary version of the square-lattice
-state Potts antiferromagnet, with
real, motivated by the fact that the continuum limit of the corresponding bulk model is a non-compact CFT, closely related with the
Euclidian black-hole coset model. While various types of conformal boundary conditions (discrete and continuous branes) have been formally identified for the the
algebra. The second type of CBC - which corresponds to restricting the values of the Potts spins to a subset of size
, or its complement of size
, at alternating sites along the boundary - is new, and turns out to be conformal in the antiferromagnetic case only. Using algebraic and numerical techniques, we show that the corresponding spectrum generating functions produce all the characters of discrete representations for the coset CFT. The normalizability bounds of the associated discrete states in the coset CFT are found to have a simple interpretation in terms of boundary phase transitions in the lattice model. For
, with
integer, we show also how our boundary conditions can be reformulated in terms of a RSOS height model. The spectrum generating functions are then identified with string functions of the compact
parafermion theory (with symmetry
). The new alt conditions are needed to cover all the string functions.
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