Entanglement phase transition in holographic pseudo entropy

We propose a new formula for computing holographic Renyi entropies in the presence of multiple extremal surfaces. Our proposal is based on computing the wave function in the basis of fixed-area states and assuming a diagonal approximation for the Renyi entropy. For Renyi index n ≥ 1, our proposal agrees with the existing cosmic brane proposal for holographic Renyi entropy. For n < 1, however, our proposal predicts a new phase with leading order (in Newton’s constant G) corrections to the cosmic brane proposal, even far from entanglement phase transitions and when bulk quantum corrections are unimportant. Recast in terms of optimization over fixed-area states, the difference between the two proposals can be understood to come from the order of optimization: for n < 1, the cosmic brane proposal is a minimax prescription whereas our proposal is a maximin prescription. We demonstrate the presence of such leading order corrections using illustrative examples. In particular, our proposal reproduces existing results in the literature for the PSSY model and high-energy eigenstates, providing a universal explanation for previously found leading order corrections to the n < 1 Renyi entropies.

We introduce a novel class of phase transitions separating quantum states with different entanglement features. An example of such an "entanglement phase transition" is provided by the many-body localization transition in disordered quantum systems, as it separates highly entangled thermal states at weak disorder from many-body localized states with low entanglement at strong disorder. In the spirit of random matrix theory, we describe a simple model for such transitions where a physical quantum many-body system lives at the "holographic" boundary of a bulk random tensor network. Using a replica trick approach, we map the calculation of the entanglement properties of the boundary system onto the free energy cost of fluctuating domain walls in a classical statistical mechanics model. This allows us to interpret transitions between volume-law and area-law scaling of entanglement as ordering transitions in this statistical mechanics model. Our approach allows us to get an analytic handle on the field theory of these entanglement transitions.

Entanglement phase transitions in hybrid quantum circuits describe individual quantum trajectories rather than the measurement-averaged ensemble, despite the fact that results of measurements are not conventionally used for feedback. Here, we numerically demonstrate that a class of generalized measurements with identical measurement-averaged dynamics give different phases and phase transitions. We show that measurement-averaged destruction of Bell state entanglement is a useful proxy for determining which hybrid circuit yields the lowest-entanglement dynamics. We use this to argue that no unfolding of our model can avoid a volume law phase, which has implications for simulation of open quantum systems.

We investigate the entanglement dynamics of the non-Hermitian Aubry-Andr\'e-Harper chain. The results reveal that by increasing quasiperiodic strength, a phase transition occurs from the area law induced by non-Hermitian skin effect to the area law arising from Anderson localization. For the former, the entanglement entropy follows a nonmonotonic process, i.e., it increases first, then oscillates, and finally converges to a stable value while, for the latter, the entanglement entropy remains low because the wave function is not expandable in Anderson's localization region. The early-stage behavior of entanglement entropy indicates that the two area-law cases are of different phases. Interestingly, the volume-law behavior emerges at the critical point between these two area-law phases. Our study reveals that the area laws induced by the skin effect and the Anderson localization are two different phases, and that a volume law can emerge at the phase transition point. The understanding of the entanglement phase transition induced by disorder and skin effect is thus deepened.

Despite its fully unitary dynamics, the bosonic Kitaev chain (BKC) displays key hallmarks of non-Hermitian physics, including nonreciprocal transport and the non-Hermitian skin effect. Here, we demonstrate another remarkable phenomena: the existence of an entanglement phase transition (EPT) in a variant of the BKC that occurs as a function of a Hamiltonian parameter g and which coincides with a transition from a reciprocal to a nonreciprocal phase. As g is reduced below a critical value, the postquench entanglement entropy of a subsystem of size l goes from a volume-law phase, where it scales as l, to a -law phase, where it scales like lN, where N is the total system size. This EPT occurs for a system undergoing purely unitary evolution and does not involve measurements, postselection, disorder, or dissipation. We derive analytically the entanglement entropy out of and at the critical point for the cases of l=1 and l/N≪1. Published by the American Physical Society 2024

We study a class of quantum states involving multiple entangled CFTs in AdS3/CFT2, associated with multi-boundary black hole geometries, and demonstrate that the Ryu-Takayanagi (RT) formula for entanglement entropy can be derived using only boundary CFT data. Approximating the OPE coefficients by their Gaussian moments within the 2D large-c CFT ensemble, we show that both the norm of the states and the entanglement entropies associated with various bipartitions — reproducing the expected bulk dual results — can be computed purely from the CFT. All macroscopic geometric structures arising from gravitational saddles emerge entirely from the universal statistical moments of the microscopic algebraic CFT data, revealing a statistical-mechanical mechanism underlying semiclassical gravity. We establish a precise correspondence between the CFT norm, the Liouville partition function with ZZ boundary conditions, and the exact gravitational path integral over 3D multi-boundary black hole geometries. For entanglement entropy, each RT phase arises from a distinct leading-order Gaussian contraction, with phase transitions — analogous to replica wormholes — emerging naturally from varying dominant statistical patterns in the CFT ensemble. Our derivation elucidates how the general mechanism behind holographic entropy, namely a boundary replica direction that elongates and becomes contractible in the bulk dual, is encoded explicitly in the statistical structure of the CFT data.

Vibrational entropy is important for the thermodynamics of alloying, alloy formation, phase transitions and phase stability at high temperature. Vibrational entropies of alloying and alloy formation were calculated for 32 binary alloys and intermetallic compounds using phonon DOS curves taken from the literature. The vibrational entropies of formation span a wide range from -0.64 to +0.55 kB/atom, and the vibrational entropies of alloying ranged from -0.39 to +1.0 kB/atom. This range exceeds the range of configurational entropy of a binary alloy, which reaches a maximum value of +0.69 kB/atom and a minimum value of 0 kB/atom. The vibrational entropy of the NiTi martensitic transition was measured using low-temperature calorimetry and inelastic neutron-scattering. The high-temperature B2 phase of NiTi has a vibrational entropy 0.5 kB/atom larger than the low-temperature martensitic phase. The difference in vibrational entropy accounts for the total entropy of the austenitic-martensitic phase transition. Inelastic neutron scattering was used to show that the phonon DOS of V is unchanged between 20 and 1000°C, inconsistent with the phonon softening expected from thermal expansion. It is found that the effects of volume expansion and rising temperature exert equal and opposite shifts on the phonon DOS. The pure temperature dependence of the phonon DOS is due to strong phonon-phonon scattering, which in turn leads to a large anharmonic vibrational entropy contribution at high temperature. The vibrational entropy of eight chemically disordered Cu-Au alloys was measured using inelastic neutron scattering. The analysis of the phonon entropy of a disordered alloy was performed in a novel way by modeling the partial vibrational entropies of Cu and Au. The partial vibrational entropies of Cu and Au were shown to be slowly varying and smooth functions of composition. The vibrational entropy of disordering in Cu3Au is calculated as 0.24 ± 0.02 kB/atom, substantially larger than results predicted from recent theoretical work.

The Standard Model and its extensions predict multiple phase transitions in the early universe. In addition to the electroweak phase transition, one or several of these could occur at energies close to the weak scale. Such phase transitions can leave their imprint on the relic abundance of TeV-scale dark matter. In this paper, we enumerate several physical features of a generic phase transition and parameterize the effect of each on the relic abundance. In particular, we include among these effects the presence of the scalar field vacuum energy and the cosmological constant, which is sensitive to UV physics. Within the context of the Standard Model Higgs sector, we find that the relic abundance of generic TeV-scale dark matter is affected by the vacuum energy at the order of a fraction of a percent. For scalar field sectors with strong first order phase transitions, an order one percent apparent tuning of coupling constants may allow corrections induced by the vacuum energy to be of order unity.

The nonlinear σ-model with the Wess-Zumino action describes the nucleon as a soliton and incorporates the non-abelian chiral anomalies. Several studies have shown that the model works well except for the nucleon mass, which comes out consistently too large. We investigate this question beginning with the more general framework of the linear σ-model, which has besides a pseudoscalar meson sector, a fermion or quark sector, a scalar field and an interaction between the fermions via the scalar field. Using a path integral formulation, we express the fermion measure of the model as the product of a Jacobian and an invariant measure. Identifying this Jacobian as exp[iΓwz] , we find that the model breaks up into two parts, when in the pseudoscalar meson sector the scalar field is replaced by its vacuum value. The pseudoscalar part of the model becomes the nonlinear σ-model with the Wess-Zumino actionΓwz. The other part involves chiral fermions, the scalar field and their interaction. We continue this part back to the Minkowski space to determine its ground state and energy levels. We find that for a scalar field that vanishes at smallr, but rises sharply to its vacuum value at someR, the ground state energy of the interacting quark-scalar-field system can be lower than the ground state energy of the non-interacting quark system. This means the interaction between quarks and the scalar field can lead to a condensed ground state or vacuum and can reduce the overall energy of the system (a phase transition as in superconductivity). It is, therfore, not surprising that the nonlinear σ-model predicts too large a nucleon mass, since it implicitly assumes a normal non-interacting vacuum in the quark sector. Quarks are now quasiparticles that appear as excitations of the condensed vacuum. The nucleon structure that emerges from this investigation agrees fully with the phenomenological nucleon structure found from analysis of high energy elasticpp and\(\bar p\)p scattering at CERN ISR and SPS Collider.

An analytic treatment of the one Higgs doublet, electroweak phase transition is given. The phase transition is first order, occurs by the nucleation of thin walled bubbles and completes at a temperature where the order parameter, {l angle}{phi}{r angle}{sub T} is significantly smaller than it is when the origin becomes absolutely unstable. The rate of anomalous baryon number violation is an exponentially function of {l angle}{phi}{r angle}{sub T}. In very minimal extensions of the standard model it is quite easy to increase {l angle}{phi}{r angle}{sub T} so that anomalous baryon number violation is suppressed after completion of the phase transition. Hence baryogenesis at the electroweak phase transition is tenable in minimal of the standard model. In some cases additional phase transitions are possible. For a light Higgs boson, when the top quark mass is sufficiently large, the state where the Higgs field has a vacuum expectation value {l angle}{phi}{r angle} = 246 GeV is not the true minimum of the Higgs potential. When this is the case, and when the top quark mass exceeds some critical value, thermal fluctuations in the early universe would have rendered the state {l angle}{phi}{r angle} = 246 GeV unstable. The requirement that the statemore » {l angle}{phi}{r angle} = 246 GeV is sufficiently long lived constrains the masses of the Higgs boson and the top quark. Finally, we consider whether local phase transitions can be induced by heavy particles which act as seeds for deformations in the scalar field.« less

Hot hypernuclear matter is investigated in an explicit SU(3) quark model based on a mean field description of nonoverlapping baryon bags bound by the self-consistent exchange of scalar $\sigma, \zeta$ and vector $\omega, \phi$ mesons. The $\sigma, \omega$ mean fields are assumed to couple to the u,d-quarks while the $\zeta, \phi$ mean fields are coupled to the s-quark. The coupling constants of the mean fields with the quarks are assumed to satisfy SU(6) symmetry. The calculations take into account the medium dependence of the bag parameter on the scalar fields $\sigma, \zeta$. We consider only the octet baryons $N,\Lambda,\Sigma,\Xi$ in hypernuclear matter. An ideal gas of the strange mesons $K$ and $K^{*}$ is introduced to keep zero net strangeness density. Our results for symmetric hypernuclear matter show that a phase transition takes place at a critical temperature around 180 MeV in which the scalar mean fields $\sigma, \zeta$ take nonzero values at zero baryon density. Furthermore, the bag contants of the baryons decrease significantly at and above this critical temperature indicating the onset of quark deconfinement. The present results imply that the onset of quark deconfinement in SU(3) hypernuclear matter is much stronger than in SU(2) nuclear matter.

The work compiles a correlated study of a gravitational quasi equilibrium thermodynamic approach for establishing and signifying a unique behavior of the cosmological entropy and phase transitions in an expanding Universe. On the basis of prescribed boundary conditions for the cluster temperature a relation for the intra‐cluster medium (ICM) of galaxy clusters has been derived. A more productive and signifying approach of the correlation functions used for galaxy clustering phenomena shows a unique behavior of the entropy change where a phenomenon known as the gravitational phase transition occurs. This unique behavior occurs with a symmetry breaking from mild clustering to low clustering and from mild clustering to high clustering which differs from a normal symmetry breaking in material sciences. We also derive results for the specific latent heat associated with the phase transitions of 3.20 Tc and 0.55 Tc for the mildly clustered phase to the low clustered phase and from the mildly clustered phase to the highly clustered phase, respectively. (© 2015 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Role of metal fluoride octahedra in the mechanism of phase transitions in A 2BMF 6 elpasolites

The freeze-in mechanism describes the out-of-equilibrium production of dark matter (DM) particles via feeble couplings or non-renormalisable interactions with large suppression scales. In the latter case, predictions suffer from a strong sensitivity to the initial conditions of the universe, such as the details of reheating. In this work, we investigate how this sensitivity is altered in the presence of a cosmological first-order phase transition. We show that freeze-in via non-renormalisable interactions is not always dominated by the highest temperatures of the Standard Model (SM) thermal bath, but instead may be governed by the period immediately after the phase transition, during which the decaying scalar field transfers its energy density to the SM radiation. We refer to this alternative production regime as DM phase-in. Using numerical and approximate analytical solutions of the relevant Boltzmann equations, we determine the conditions under which phase-in or conventional freeze-in production dominates the final DM abundance in terms of the type of interaction between the DM and SM particles, the amount of supercooling before and the evolution of the scalar field after the phase transition. In the phase-in regime, the DM abundance is correlated with the peak frequency of the gravitational wave signal associated with the phase transition, opening up new observational possibilities.

Scalar field model applied to the lamellar to the inverse hexagonal phase transition in lipid systems