33,713 research outputs found
Quantum Kibble-Zurek mechanism and critical dynamics on a programmable Rydberg simulator
Quantum phase transitions (QPTs) involve transformations between different
states of matter that are driven by quantum fluctuations. These fluctuations
play a dominant role in the quantum critical region surrounding the transition
point, where the dynamics are governed by the universal properties associated
with the QPT. While time-dependent phenomena associated with classical,
thermally driven phase transitions have been extensively studied in systems
ranging from the early universe to Bose Einstein Condensates, understanding
critical real-time dynamics in isolated, non-equilibrium quantum systems is an
outstanding challenge. Here, we use a Rydberg atom quantum simulator with
programmable interactions to study the quantum critical dynamics associated
with several distinct QPTs. By studying the growth of spatial correlations
while crossing the QPT, we experimentally verify the quantum Kibble-Zurek
mechanism (QKZM) for an Ising-type QPT, explore scaling universality, and
observe corrections beyond QKZM predictions. This approach is subsequently used
to measure the critical exponents associated with chiral clock models,
providing new insights into exotic systems that have not been understood
previously, and opening the door for precision studies of critical phenomena,
simulations of lattice gauge theories and applications to quantum optimization
Defect scaling Lee-Yang model from the perturbed DCFT point of view
We analyze the defect scaling Lee-Yang model from the perturbed defect
conformal field theory (DCFT) point of view. First the defect Lee-Yang model is
solved by calculating its structure constants from the sewing relations.
Integrable defect perturbations are identified in conformal defect perturbation
theory. Then pure defect flows connecting integrable conformal defects are
described. We develop a defect truncated conformal space approach (DTCSA) to
analyze the one parameter family of integrable massive perturbations in finite
volume numerically. Fusing the integrable defect to an integrable boundary the
relation between the IR and UV parameters can be derived from the boundary
relations. We checked these results by comparing the spectrum for large volumes
to the scattering theory.Comment: LaTeX, 33 pages, 9 figures, figures adde
Static and dynamic lengthscales in a simple glassy plaquette model
We study static and dynamic spatial correlations in a two-dimensional spin
model with four-body plaquette interactions and standard Glauber dynamics by
means of analytic arguments and Monte Carlo simulations. We study in detail the
dynamical behaviour which becomes glassy at low temperatures due to the
emergence of effective kinetic constraints in a dual representation where spins
are mapped to plaquette variables. We study the interplay between non-trivial
static correlations of the spins and the dynamic `four-point' correlations
usually studied in the context of supercooled liquids. We show that slow
dynamics is spatially heterogeneous due to the presence of diverging
lengthscales and scaling, as is also found in kinetically constrained models.
This analogy is illustrated by a comparative study of a froth model where the
kinetic constraints are imposed.Comment: 12 pages, 13 figs; published versio
Probing defects and correlations in the hydrogen-bond network of ab initio water
The hydrogen-bond network of water is characterized by the presence of
coordination defects relative to the ideal tetrahedral network of ice, whose
fluctuations determine the static and time-dependent properties of the liquid.
Because of topological constraints, such defects do not come alone, but are
highly correlated coming in a plethora of different pairs. Here we discuss in
detail such correlations in the case of ab initio water models and show that
they have interesting similarities to regular and defective solid phases of
water. Although defect correlations involve deviations from idealized
tetrahedrality, they can still be regarded as weaker hydrogen bonds that retain
a high degree of directionality. We also investigate how the structure and
population of coordination defects is affected by approximations to the
inter-atomic potential, finding that in most cases, the qualitative features of
the hydrogen bond network are remarkably robust
Entanglement Entropy in Integrable Field Theories with Line Defects II. Non-topological Defect
This is the second part of two papers where we study the effect of integrable
line defects on bipartite entanglement entropy in integrable field theories. In
this paper, we consider non-topological line defects in Ising field theory. We
derive an infinite series expression for the entanglement entropy and show that
both the UV and IR limits of the bulk entanglement entropy are modified by the
line defect. In the UV limit, we give an infinite series expression for the
coefficient in front of the logarithmic divergence and the exact defect
-function. By tuning the defect to be purely transmissive and reflective, we
recover correctly the entanglement entropy of the bulk and with integrable
boundary.Comment: 30 pages, references added, typos corrected, publication versio
Error threshold in optimal coding, numerical criteria and classes of universalities for complexity
The free energy of the Random Energy Model at the transition point between
ferromagnetic and spin glass phases is calculated. At this point, equivalent to
the decoding error threshold in optimal codes, free energy has finite size
corrections proportional to the square root of the number of degrees. The
response of the magnetization to the ferromagnetic couplings is maximal at the
values of magnetization equal to half. We give several criteria of complexity
and define different universality classes. According to our classification, at
the lowest class of complexity are random graph, Markov Models and Hidden
Markov Models. At the next level is Sherrington-Kirkpatrick spin glass,
connected with neuron-network models. On a higher level are critical theories,
spin glass phase of Random Energy Model, percolation, self organized
criticality (SOC). The top level class involves HOT design, error threshold in
optimal coding, language, and, maybe, financial market. Alive systems are also
related with the last class. A concept of anti-resonance is suggested for the
complex systems.Comment: 17 page
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