arXiv subjects

Himanshu Parihar

Publications and source records attributed to Himanshu Parihar.

At least 19 recordsLinked to original sources

arXiv2026

Anomaly Induced Current in Boundary Lifshitz Field Theory

We study quantum transport phenomena induced by anisotropic Lifshitz scale anomaly in a boundary Lifshitz field theory (BLFT) coupled to an external electromagnetic background. In this context, we obtain the anisotropic scale anomaly in Lifshitz field theories coupled to a background $U(1)$ gauge field and subsequently compute the anomaly induced near boundary current in a BLFT. Focusing on 5D BLFTs, we find that the temporal and spatial components of the induced current exhibit distinct power law dependencies on the distance from the boundary, reflecting the intrinsic time-space anisotropy of the theory. We further derive this anomalous current holographically from the bulk dual of BLFT and find that the temporal component is independent of the boundary conditions while the spatial component depends explicitly on them. The distance dependence is in exact agreement with the dual field theory result.

hep-th↗

arXiv2026

Holographic Entanglement Negativity and Thermodynamics in Backreacted AdS Black Hole

We investigate holographic entanglement negativity (HEN) as a probe of mixed state quantum correlations in a deformed AdS black hole background with backreaction sourced by a string cloud. The bulk geometry is dual to a strongly coupled large-$N_c$ gauge theory at finite temperature, backreacted by a finite density of heavy static fundamental quarks. We analyze entanglement thermodynamics and establish a first law like relation in the small backreaction regime by identifying the deformed black hole at zero temperature as the natural ground state of the dual field theory. Using analytic expansions in the low and high temperature limits, we compute the HEN for adjacent, bipartite and disjoint subsystem configurations and examine its dependence on the backreaction parameter $ρ$. Our results reveal that at low temperature and high effective temperature, backreaction increases the HEN signaling enhancement of distillable quantum correlations. We further compare the behavior of HEN with holographic entanglement entropy (HEE) and mutual information (MI), demonstrating that entanglement negativity provides a sharper diagnostic of the competition between thermal and quantum correlations in holographic plasmas with matter backreaction.

hep-th↗

arXiv2025

Timelike entanglement entropy with gravitational anomalies

We study the timelike entanglement entropy (TEE) in two dimensional conformal field theories (CFT) with gravitational anomalies. We employ analytical continuation to compute the timelike entanglement entropy for a pure timelike interval in such CFTs. We find that, unlike the real part, the imaginary part of the TEE displays an asymmetric dependence on the central charges of the left and right moving modes. We propose that the asymmetric dependence on central charges of the imaginary part of the TEE can be used to probe the presence of gravitational anomalies in chiral CFT. Furthermore, we propose a holographic construction to obtain the timelike entanglement entropy from the bulk dual geometries involving topologically massive gravity in AdS$_3$. The holographic results obtained match exactly with the dual field theory results.

hep-th↗

arXiv2025

Charged Black Hole with String Cloud Deformation: Entanglement and Chaos

We perform a holographic analysis of several quantum information theoretic observables entanglement entropy (EE), mutual information (MI), entanglement wedge cross section (EWCS), butterfly velocity ($v_B$) and thermo mutual information (TMI) in the background of charged AdS black hole deformed by a homogeneous string cloud. This configuration is dual to a large $\mathcal{N}_c$ strongly coupled field theory at finite temperature and finite chemical potential, in presence of quark cloud. We study how the entanglement structure and chaotic dynamics in the boundary theory are affected by the charge and backreaction. We find that both EE and EWCS increase monotonically with charge and backreaction, indicating enhanced correlations due to additional bulk degrees of freedom. On the other hand MI and TMI show a more intricate dependence backreaction tends to strengthen correlations, while increasing charge suppresses entanglement and makes the system more susceptible to scrambling. The analysis of the butterfly velocity indicates that both the presence of charge and the backreaction suppress the chaotic behavior of the system by reducing $v_B$. Furthermore, TMI exhibits a sharp transition under shockwave perturbations, with inter-boundary entanglement being entirely disrupted beyond a critical shock strength, which decreases with increasing charge.

hep-th↗

arXiv2025

Effect of backreaction on Island, Page curve and Mutual Information

We compute the entanglement entropy of Hawking radiation in a bath attached to a deformed eternal AdS black hole. This black hole is dual to the two identical strongly coupled large-$N_c$ thermal field theories, where each theory is backreacted (deformed) by the presence of a uniform static distribution of heavy fundamental quarks. In our observation we find that the entanglement entropy of Hawking radiation increases in a quadratic manner for an early time and linearly for the late time. The large time expression for the entanglement entropy of Hawking radiation is used to find the Page curve and Page time. After the Page time, the entanglement entropy saturates to a constant value due to the appearance of an island. We observe that introducing deformation (backreaction) delays the appearance of island and shifts the Page curve to a later time. Subsequently, the computation of the scrambling time reveals an increase with the backreaction parameter, suggesting a longer duration for information retrieval in the presence of deformation. Moreover, our analysis of the mutual information between the radiation subsystems shows that it vanishes at a critical time which increases with the deformation before the Page time. After the Page time, the appearance of island leads to the vanishing of mutual information between black hole subsystems and gives the time difference of the order of scrambling time.

hep-th↗

arXiv2025

Mixed state entanglement in deformed field theory at finite temperature

We study mixed state entanglement measures in a higher dimensional $T\bar{T}$ deformed field theory at finite temperature. The holographic dual is described by AdS$_{d+1}$ black brane geometry with a finite cutoff. We compute the entanglement wedge cross section (EWCS), proposed to be dual to entanglement of purification (EoP) and holographic entanglement negativity (HEN) for strip like subsystems. The behavior of EWCS and HEN is studied across different regimes of temperature and deformation parameter. It is observed that the deformation and temperature exhibit similar effects on these two entanglement measures. Increasing the deformation leads to a decrease in the entanglement between the subsystems.

hep-th↗

arXiv2024

Holographic entanglement negativity for disjoint subsystems in $\mathrm{AdS_{d+1}/CFT_d}$

We propose a construction to compute the holographic entanglement negativity for bipartite mixed state configurations of two disjoint subsystems in higher dimensional conformal field theories (CFT$_d$s) dual to bulk AdS$_{d+1}$ geometries. Our proposal follows from the corresponding AdS$_3$/CFT$_2$ scenario and involves an algebraic sum of the areas of bulk RT surfaces for certain combinations of subsystems. Utilizing our construction we compute the holographic entanglement negativity at the leading order through a perturbative expansion, for such bipartite mixed states of two disjoint subsystems with long rectangular strip geometries in CFT$_d$s dual to bulk pure AdS$_{d+1}$ geometries and AdS$_{d+1}$-Schwarzschild black holes.

hep-th↗

arXiv2024

Holography for Boundary Lifshitz Field Theory

We propose a holographic duality for the boundary Lifshitz field theory (BLFT). Similar to holographic BCFT, holographic BLFT can be consistently defined by imposing either a Neumann boundary condition (NBC) or a conformal boundary condition (CBC) on the end of the world (EOW) brane. We propose $g$-functions and derive $g$-theorem for these two types of holographic BLFT. On the field theory side, we consider BLFT whose path integral is prescribed to include also paths bouncing off the boundary. The entanglement entropy for an interval for the Lifshitz invariant ground state is computed in the saddle point approximation, and is found to agree precisely with the holographic result in both limits when the interval is very close or very far away from the boundary.

hep-th↗

arXiv2024

Massless Lifshitz Field Theory for Arbitrary $z$

By using the notion of fractional derivatives, we introduce a class of massless Lifshitz scalar field theory in (1+1)-dimension with an arbitrary anisotropy index $z$. The Lifshitz scale invariant ground state of the theory is constructed explicitly and takes the form of Rokhsar-Kivelson (RK). We show that there is a continuous family of ground states with degeneracy parameterized by the choice of solution to the equation of motion of an auxiliary classical system. The quantum mechanical path integral establishes a 2d/1d correspondence with the equal time correlation functions of the Lifshitz scalar field theory. We study the entanglement properties of the Lifshitz theory for arbitrary $z$ using the path integral representation. The entanglement measures are expressed in terms of certain cross ratio functions we specify, and satisfy the $c$-function monotonicity theorems. We also consider the holographic description of the Lifshitz theory. In order to match with the field theory result for the entanglement entropy, we propose a $z$-dependent radius scale for the Lifshitz background. This relation is consistent with the $z$-dependent scaling symmetry respected by the Lifshitz vacuum. Furthermore, the time-like entanglement entropy is determined using holography. Our result suggests that there should exist a fundamental definition of time-like entanglement other than employing analytic continuation as performed in relativistic field theory.

hep-th↗

arXiv2024

Change of polarization degree of light beams on propagation in curved space

Even in free space, which is commonly considered of as a flat space-time in most settings, the degree of polarization of a partially spatially coherent light beam changes as it travels. Similarly, the polarization degree would change when a partially spatially coherent light beam propagates in a curved space-time. The difference of the polarization degree between the curved space and flat space can reveal the essential structure of the curved space. In this work, we consider a simplest case of curved space known as Schwarzschild spacetime. We can simulate the Schwarzschild space-time as an optical material with an effective refractive index. The difference of the polarization degree of a light beam propagating in curved space and flat space can be achieved up to $ 5\% $, which is detectable in practical measurement. In addition, we have found that the partially spatially coherent light source is necessary for obtaining significant changes in polarization degree. Our results provide an alternative method to estimate the Schwarzschild radius of a massive object with the optical polarization degree measurement.

physics.optics↗

arXiv2024

On minimal entanglement wedge cross section for holographic entanglement negativity

We demonstrate the equivalence of two different conjectures in the literature for the holographic entanglement negativity in AdS$_3$/CFT$_2$, modulo certain constants. These proposals involve certain algebraic sums of bulk geodesics homologous to specific combinations of subsystems, and the entanglement wedge cross section (EWCS) backreacted by a cosmic brane for the conical defect geometry in the bulk gravitational path integral. It is observed that the former conjectures reproduce the field theory replica technique results in the large central charge limit whereas the latter involves constants related to the Markov gap. In this context we establish an alternative construction for the EWCS of a single interval in a CFT$_2$ at a finite temperature to resolve an issue for the latter proposal involving the thermal entropy elimination for the holographic entanglement negativity. Our construction for the EWCS correctly reproduces the corresponding field theory results modulo the Markov gap constant in the large central charge limit.

hep-th↗

arXiv2023

Holographic Reflected Entropy and Islands in Interface CFTs

We investigate the reflected entropy for various mixed state configurations in the two dimensional holographic conformal field theories sharing a common interface (ICFTs). In the AdS$_3$/ICFT$_2$ framework, we compute the holographic reflected entropy for the required configurations in the vacuum state of the ICFT$_{\text{2}}$ which is given by twice the entanglement wedge cross section (EWCS) in a spacetime involving two AdS$_3$ geometries glued along a thin interface brane. Subsequently, we evaluate the EWCS in the bulk geometry involving eternal BTZ black strings with an AdS$_2$ interface brane, which is dual to an ICFT$_2$ in the thermofield double (TFD) state. We explore the system from a doubly holographic perspective and determine the island contributions to the reflected entropy in the two dimensional semi-classical description involving two CFT$_{\text{2}}$s coupled to an AdS$_2$ brane. We demonstrate that the results from the island formula match precisely with the bulk AdS$_3$ results in the large tension limit of the interface brane. We illustrate that the phase structure of the reflected entropy is quite rich involving many novel induced island phases and demonstrate that it obeys the expected Page curve for the reflected entropy in a radiation bath coupled to the AdS$_2$ black hole.

hep-th↗

arXiv2023

Time-like Entanglement Entropy in AdS/BCFT

We study the entanglement entropy for time-like subsystem in two-dimensional boundary conformal field theory (BCFT) both from the field theory and holographic point of view. In field theory, we compute the time-like entanglement entropy of a pure time-like interval at zero and finite temperature using the replica technique and analytical continuation. We find that, similar to the ordinary space-like entanglement entropy in BCFT, the time-like entropy also has a bulk phase and a boundary phase which corresponds respectively to the dominance of the identity block in the bulk and boundary OPE channels. However, we find that in Lorentzian BCFT, the time-like entanglement entropy posses a third {\it Regge phase} which arises in the Regge limit of the interval, when one endpoint of the time interval approaches the light cone of the mirror image of the other endpoint. We determine the phase diagram for the time-like entanglement entropy. We find that while the time-like entropy is complex in the bulk phase and has a boundary term in the boundary phase, there is no boundary entropy in the Regge phase. Moreover, it can be real or complex depending on which side the Regge limit is approached from. On the gravity side, we obtain the holographic time-like entanglement entropy from the corresponding bulk dual geometries and find exact agreement with the field theory results. The time-like entanglement entropy may be useful to describe the entanglement of a quantum dot on a half line.

hep-th↗

arXiv2022

Entanglement negativity, reflected entropy, and anomalous gravitation

We investigate mixed state entanglement measures of entanglement negativity and reflected entropy for bipartite states in two dimensional conformal field theories with an anomaly through appropriate replica techniques. Furthermore we propose holographic constructions for these measures from the corresponding bulk dual geometries involving topologically massive gravity in AdS$_3$ and find exact agreement with the field theory results. In this connection we extend an earlier holographic proposal for the entanglement negativity to the bulk action with a gravitational Chern-Simons term and compute its contribution to the entanglement wedge cross section dual to the reflected entropy.

hep-th↗

arXiv2022

Reflected Entropy and Entanglement Negativity for Holographic Moving Mirrors

We investigate the time evolution of reflected entropy and entanglement negativity for mixed state configurations involving two adjacent and disjoint intervals in the radiation flux of moving mirrors by utilizing the $AdS/BCFT$ duality. These measures are computed for the required mixed state configurations by using the respective replica techniques in the large central charge limit of the $BCFT_{1+1}$. We demonstrate that the results obtained exactly agree with the corresponding holographic computations in the dual bulk $AdS_3$ geometry with an end of the world brane. In this context, the analogues of the Page curves for these measures are obtained for the required configurations in the radiation flux of kink and escaping mirrors which mimic the Hawking radiation from evaporating and eternal black holes respectively.

hep-th↗

arXiv2022

Defect extremal surfaces for entanglement negativity

We propose a doubly holographic version of the semi-classical island formula for the entanglement negativity in the framework of the defect AdS/BCFT correspondence where the AdS bulk contains a defect conformal matter theory. In this context, we propose a defect extremal surface (DES) formula for computing the entanglement negativity modified by the contribution from the defect matter theory on the end-of-the-world brane. The equivalence of the DES proposal and the semi-classical island formula for the entanglement negativity is demonstrated in AdS$_3$/BCFT$_2$ framework. Furthermore, in the time-dependent AdS$_3$/BCFT$_2$ scenarios involving eternal black holes in the lower dimensional effective description, we investigate the time evolution of the entanglement negativity through the DES and the island formulae and obtain the analogues of the Page curves.

hep-th↗

arXiv2022

Entanglement Negativity in Flat Holography

We advance holographic constructions for the entanglement negativity of bipartite states in a class of $(1+1)-$dimensional Galilean conformal field theories dual to asymptotically flat three dimensional bulk geometries described by Einstein Gravity and Topologically Massive Gravity. The construction involves specific algebraic sums of the lengths of bulk extremal curves homologous to certain combinations of the intervals appropriate to such bipartite states. Our analysis exactly reproduces the corresponding replica technique results in the large central charge limit. We substantiate our construction through a semi classical analysis involving the geometric monodromy technique for the case of two disjoint intervals in such Galilean conformal field theories dual to bulk Einstein Gravity.

hep-th↗

arXiv2022

Covariant holographic negativity from the entanglement wedge in AdS$_3/$CFT$_2$

We propose a covariant holographic construction based on the extremal entanglement wedge cross section, for the entanglement negativity of bipartite states in $CFT_{1+1}$s dual to non static bulk $AdS_3$ geometries. Utilizing our proposal we obtain the holographic entanglement negativity for bipartite mixed states in $CFT_{1+1}$s dual to bulk extremal and non extremal rotating BTZ black holes and the time dependent Vaidya-$AdS_3$ geometries. Our results correctly reproduce the replica technique results modulo certain constants for the corresponding dual $CFT_{1+1}$s in the large central charge limit for the bulk black hole geometries. Furthermore for all the cases our results also match upto such constants with the corresponding results from an earlier alternate covariant holographic construction in the literature. This demonstrates the equivalence modulo constants of the two constructions for the $AdS_3/CFT_2$ scenario.

hep-th↗