Holographic Subregion Complexity Research Articles

Holographic entanglement entropy and subregion complexity for s-wave superconductor from massive gravity

In this paper, in the framework of massive gravity, the holographic entanglement entropy (HEE) and holographic subregion complexity (HSC) are numerically investigated by means of the RT formula and the subregion CV conjucture for holographic superconductor with backreaction. We find that both the HEE and HSC exhibit discontinuity of slope at critical temperature, hence both of them are able to reflect the information of phase transition in the holographic superconducting system. Different from the previous studies, the HEE and HSC as function of strip-width are not always lower in the superconducting phase than ones in the normal phase, in particular the HSC decreases linearly as the subregion increases for positive coupling parameters. We notice that when the coupling parameters α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} and β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta $$\\end{document} are taken as positive values, the HSC behaves in the same way as HEE, but when they are negative, the HSC has many different behaviors from HEE. Furthermore, we also observe that the HEE and HSC in the superconducting phase illustrate a tendency to converge to the same value as the temperature approaches zero, regardless of the coupling parameters of model. It is worth mentioning that in the massless gravity limit (the coupling parameters α=0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha =0$$\\end{document} and β=0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta =0$$\\end{document}), the results given by us are consistent with the case of holographic superconductor with backreaction from Einstein gravity.

Resource and stability near a critical point from the quantum information perspective

In the presence of chemical potential and temperature, we holographically study subregion complexity in a non-conformal quantum field theory with a critical point. We propose a new interpretation according to which the states, needing (more) less information to be specified, characterize the (un) stable thermodynamical solutions. We observe the increasing and decreasing effects of chemical potential and temperature on holographic subregion complexity, respectively. These two opposite behaviors lead to a point where subregion complexity of the mixed state is the same as this value for a zero temperature conformal field theory. We also present a new description of the difference between the minimum and the maximum value (the value near the critical point) of holographic subregion complexity as a resource for doing computational work to prepare the state near the critical point from the state far from it. We also calculate the critical exponent.

Holographic entanglement entropy and subregion complexity for excited states of holographic superconductors

We investigate the holographic entanglement entropy (HEE) and the holographic subregion complexity (HSC) for holographic superconductors, both in the Einstein and in the Einstein-Gauss-Bonnet gravitational theories. For both ground and excited states, we show that, in the Einstein gravity, the HSC decreases as the temperature increases and the normal phase has a smaller HSC than the superconducting phase, which is opposite to the behavior of the HEE. Moreover, we find out that, for a given temperature T in the superconducting phase, the higher excited state leads to a lager value of the HEE but a smaller value of the HSC. However, the Einstein-Gauss-Bonnet gravity has significantly different effect on the HSC, while the HEE always increases monotonously as the temperature increases and its value in the normal phase always larger than that in the superconducting phase. Our results indicate that the HEE and HSC provide richer physics in phase transitions and condensation of scalar hair for holographic superconductors with excited states.

Holographic entanglement entropy and complexity for D-wave superconductors

Using the RT formula and the subregion CV conjecture, we numerically investigate the holographic entanglement entropy (HEE) and holographic subregion complexity (HSC) for two holographic d-wave superconducting models with backreactions. We find that the HEE and HSC can probe these two d-wave superconducting phase transitions. The HEE of the superconducting phase is always lower than that of the normal phase. For the HSC, however, it behaves differently and interestingly, which depends on both the strip-width L_{x} and backreaction kappa . More specifically, when the backreaction is larger than a particular critical value, or the strip-width of the boundary subsystem is smaller than a particular critical value, the HSC in the superconducting phase is larger than that in the normal phase, and vice versa.

Bath deformations, islands, and holographic complexity

Considering a doubly holographic model, we study the evolution of holographic subregion complexity corresponding to deformations of bath state by a relevant scalar operator, which corresponds to a renormalization group flow from the AdS-Schwarzschild to the Kasner universe in the bulk. The subregion complexity shows a discontinuous jump at Page time at a fixed perturbation, where the discontinuity depends solely on the system's parameters. We show that the amount of discontinuity decreases with the perturbation as well as with the scaling dimension of the relevant scalar operator.

Note on stability and holographic subregion complexity

We study holographic subregion complexity in a spatially anisotropic field theory, which expresses a confinement-deconfinement phase transition. Its holographic dual is a five-dimensional anisotropic holographic model characterized by a Van der Waals-like phase transition between small and large black holes. We propose a new interpretation from the informational perspective to determine the stable and unstable thermodynamically solutions. According to this proposal, the states which need (more) less information to be specified characterize the (un) stable solutions. We similarly offer an interpretation to determine the stable and unstable solutions based on the resource of a computational machine, such that the solutions are (un) stable if computational resource (decreases) increases with the increase of temperature. We observe that the effect of anisotropy on holographic subregion complexity is decreasing. This decreasing effect can be interpreted by considering a whole closed system consisting of the state and its environment in which the complexity of the mixed state decreases and complexity of the environment increases.

Partial islands and subregion complexity in geometric secret-sharing model

We compute the holographic subregion complexity of a radiation subsystem in a geometric secret-sharing model of Hawking radiation in the “complexity = volume” proposal. The model is constructed using multiboundary wormhole geometries in AdS3. The entanglement curve for secret-sharing captures a crossover between two minimal curves in the geometry apart from the usual eternal Page curve present for the complete radiation entanglement. We compute the complexity dual to the secret-sharing minimal surfaces and study their “time” evolution. When we have access to a small part of the radiation, the complexity shows a jump at the secret-sharing time larger than the Page time. Moreover, the minimal surfaces do not have access to the entire island region for this particular case. They can only access it partially. We describe this inaccessibility in the context of “classical” Markov recovery.

Nonconformality, subregion complexity, and meson binding

We study holographically the zero and finite temperature behavior of the potential energy and holographic subregion complexity corresponding to a probe meson in a non-conformal model. We observe that in zero and low temperature non-conformality has a decreasing effect on the dimensionless meson potential energy. However, non-conformal corrections increase absolute value of the dimensionless holographic subregion complexity in both zero and finite temperature which means the non-conformal state needs less information to be specified. In other words, considering the effect of non-conformality, the less bounded meson state needs less information to be specified. In low temperature limits, thermal corrections decrease meson potential energy and do not have a specific effect on holographic subregion complexity. We find that in the vicinity of the phase transition, the zero temperature meson state is more favorable than the finite temperature state, from the holographic subregion complexity point of view.

HEE and HSC for flavors: perturbative structure in open string geometries

Introduction of electric field in the D-brane worldvolume induces a horizon in the open string geometry perceived by the brane fluctuations. We study the holographic entanglement entropy (HEE) and subregion complexity (HSC) in these asymptotically AdS geometries in three, four and five dimensions aiming to capture these quantities in the flavor sector introduced by the D-branes. Both the strip and spherical subregions have been considered. We show that the Bekenstein-Hawking entropy associated with the open string horizon, which earlier failed to reproduce the thermal entropy in the boundary, now precisely matches with the entanglement entropy at high temperatures. We check the validity of embedding function theorem while computing the HEE and attempt to reproduce the first law of entanglement thermodynamics, at least at leading order. On the basis of obtained results, we also reflect upon consequences of applying Ryu-Takayanagi proposal on these non-Einstein geometries.

Complexity and uncomplexity during energy injection

We consider a strongly coupled field theory with a critical point and nonzero chemical potential at finite temperature, which is dual to an asymptotically AdS charged black hole. We study the evolution of the rescaled holographic subregion complexity near and far from the critical point. We explain two distinct concepts of complexity in this theory and discuss that the state under study is complex based on how much information is needed to specify the state and is simple according to how many operations have to be done to reach the state. It has been reported before that time evolution of holographic subregion complexity contradicts the second law of complexity in these AdS-Vaidya-like geometries, but we try to provide a compatible interpretation. We justify decreasing of complexity using an increasing number of microstates of the mixed state and speculate about the description of the relative complexity of the initial state and the final state as a resource. We propose that in this process complexity of the mixed state decreases and complexity of the environment increases. We also observe that in this model, the rescaled holographic subregion complexity is a good observable for probing the dynamical critical exponent.

Holographic study of entanglement and complexity for mixed states

In this paper, we holographically quantify the entanglement and complexity for mixed states by following the prescription of purification. The bulk theory we consider in this work is a hyperscaling violating solution, characterized by two parameters, hyperscaling violating exponent $\theta$ and dynamical exponent $z$. This geometry is dual to a non-relativistic strongly coupled theory with hidden Fermi surfaces. We first compute the holographic analogy of entanglement of purification (EoP), denoted as the minimal area of the entanglement wedge cross section and observe the effects of $z$ and $\theta$. Then in order to probe the mixed state complexity we compute the mutual complexity for the BTZ black hole and the hyperscaling violating geometry by incorporating the holographic subregion complexity conjecture. We carry this out for two disjoint subsystems separated by a distance and also when the subsystems are adjacent with subsystems making up the full system. Furthermore, various aspects of holographic entanglement entropy such as entanglement Smarr relation, Fisher information metric and the butterfly velocity has also been discussed.

Holographic subregion complexity in unbalanced holographic superconductors

By using the subregion CV conjecture, we numerically investigate the behavior of the holographic subregion complexity (HSC) and compare it with the holographic entanglement entropy (HEE) in the unbalanced holographic superconductors, which indicates that both the HEE and HSC can be used as good probes to the phase transition in unbalanced holographic superconductors. We observe that the HEE and HSC exhibit a similar linear growth behavior with the change of width for a strip geometry. However, for different fixed widths, the HSC exhibits different behaviors with the change of the temperature, while the behavior of HEE remains consistent. In particular, we find that there are certain conditions that make it difficult to observe the phase transition of this system through the HSC approach. Furthermore, we also note that the unbalance parameter has different effects on the HSC, while the HEE always increases as the unbalance parameter increases.

Holographic subregion complexity in metal/superconductor phase transition with Born\u2013Infeld electrodynamics

We investigate the holographic subregion complexity (HSC) and compare it with the holographic entanglement entropy (HEE) in the metal/superconductor phase transition for the Born–Infeld (BI) electrodynamics with full backreaction. Based on the subregion CV conjecture, we find that the universal terms of HSC remain finite during phase transitions, and the HSC is a good probe to the critical temperature in the holographic superconducting system. Furthermore, we observe that for the operator mathcal {O}_{+}, the HSC of the superconducting phase decreases first and then increases as the BI parameter increases, which is completely different from that of HEE, and the value of the BI parameter corresponding to the inflection point of HSC is larger than that of HEE. But for the operator mathcal {O}_{-}, the HSC increases monotonically as the BI parameter increases, which is similar to that of HEE.

Universal pieces of holographic entanglement entropy and holographic subregion complexity

We propose that the definition of holographic subregion complexity (HSC) needs a slight modification for supergravity solutions with warped anti-de Sitter (AdS) factors. Such warp factors can arise due to the nontrivial dilaton profile, for example, in $AdS_6$ solutions of type IIA supergravity. This modified definition ensures that the universal piece of the HSC is proportional to that of the holographic entanglement entropy, as is the case for supergravity solutions without warp factors. This also means that the leading behaviour at large $N$ is the same for both these quantities, as we show for some well-known supergravity solutions (with and without warp factors) in various dimensions. We also show that this relation between the universal pieces suggests "universal" relations between field theoretical analogue of HSC and the sphere partition function or Weyl $a$-anomaly in odd or even dimensions, respectively.

On volume subregion complexity in non-conformal theories

We study the volume prescription of the holographic subregion complexity in a holographic 5-dimensional model consisting of Einstein gravity coupled to a scalar field with a non-trivial potential. The dual 4-dimensional gauge theory is not conformal and exhibits a RG flow between two different fixed points. In both zero and finite temperature we show that the holographic subregion complexity can be used as a measure of non-conformality of the model. This quantity exhibits also a monotonic behaviour in terms of the size of the entangling region, like the behaviour of the entanglement entropy in this setup. There is also a finite jump due to the disentangling transition between connected and disconnected minimal surfaces for holographic renormalized subregion complexity at zero temperature.

Renormalized holographic subregion complexity under relevant perturbations

We construct renormalized holographic entanglement entropy (HEE) and subregion complexity (HSC) in the CV conjecture for asymptotically AdS4 and AdS5 geometries under relevant perturbations. Using the holographic renormalization method developed in the gauge/gravity duality, we obtain counter terms which are invariant under coordinate choices. We explicitly define different forms of renormalized HEE and HSC, according to conformal dimensions of relevant operators in the d = 3 and d = 4 dual field theories. We use a general embedding for arbitrary entangling subregions and showed that any choice of the coordinate system gives the same form of the counter terms, since they are written in terms of curvature invariants and scalar fields on the boundaries. We show an explicit example of our general procedure. Intriguingly, we find that a divergent term of the HSC in the asymptotically AdS5 geometry under relevant perturbations with operators of conformal dimensions in the range 0 < ∆ < frac{1}{2} and frac{7}{2} < ∆ < 4 cannot be cancelled out by adding any coordinate invariant counter term. This implies that the HSCs in these ranges of the conformal dimensions are not renormalizable covariantly. We also write the plot of the renormalization procedure in the case of asymptotically AdSd+1 geometries, with d > 4.

Holographic information theoretic quantities for Lifshitz black hole

In this paper, we have investigated the holographic entanglement entropy for a linear subsystem in a 3+1-dimensional Lifshitz black hole. The entanglement entropy has been analysed in both the infra-red and ultra-violet limits, and has also been computed in the near horizon approximation. The notion of a generalized temperature in terms of the renormalized entanglement entropy has been introduced. This also leads to a generalized thermodynamics like law E=frac{1}{2}T_g S_{REE}. The generalized temperature has been defined in such a way that it reduces to the Hawking temperature in the infra-red limit. We find that the inverse of the generalized temperature (beta _g=1/T_g) attains a non-zero value when the subsystem length becomes zero although it is zero in case of the Schwarzschild-AdS black hole. We have then computed the holographic subregion complexity. We find that the subregion complexity has logarithmic divergence which was absent in case of the 3+1-dimensional Schwarzschild-AdS black hole. Then the Fisher information metric and the fidelity susceptibility for the same linear subsystem have also been computed using the bulk dual prescriptions. It has been observed that the two metrics are not related to each other.

Holographic subregion complexity under a thermal quench in an Einstein-Maxwell-axion theory with momentum relaxation

We investigate the evolution of holographic entanglement entropy (HEE) and holographic complexity (HC) under a thermal quench in Einstein-Maxwell-axion theory, which is dual to a field theory with momentum relaxation on the boundary. A strip-shaped boundary geometry is utilized to calculate HEE and HC via ``$\text{entropy}=\text{surface}$'' and ``$\text{complexity}=\text{volume}$'' conjecture, respectively. By fixing other parameters, we claim that either large enough black hole charge or width of the strip will introduce swallow-tail behaviors in HEE and multivalues in HC due to the discontinuity of the minimum Hubeny-Rangamani-Takayanagi surface. Meanwhile, we explore the effects of momentum relaxation on the evolution of HEE and HC. The results present that the momentum relaxation will suppress the discontinuity to occur as it increases. For large enough momentum relaxation, the continuity of HEE and HC will be recovered.

Complexity in the presence of a boundary

The effects of a boundary on the circuit complexity are studied in two dimensional theories. The analysis is performed in the holographic realization of a conformal field theory with a boundary by employing different proposals for the dual of the complexity, including the “Complexity = Volume” (CV) and “Complexity = Action” (CA) prescriptions, and in the harmonic chain with Dirichlet boundary conditions. In all the cases considered except for CA, the boundary introduces a subleading logarithmic divergence in the expansion of the complexity as the UV cutoff vanishes. Holographic subregion complexity is also explored in the CV case, finding that it can change discontinuously under continuous variations of the configuration of the subregion.

Note on holographic subregion complexity and QCD phase transition

Using holographic subregion complexity, we study the confinement-deconfinement phase transition of quantum chromodynamics. In the model we consider here, we observe a connection between the potential energy of probe meson and the behavior of its complexity. Moreover, near the critical point, at which the phase transition takes place, our numerical calculations indicate that we need less information to specify a meson in the non-conformal vacuum than in the conformal one, despite the fact that the non-conformal vacuum has larger energy!