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"Zhong, Ying"
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Critical phenomena of regular black holes in anti-de Sitter space-time
In General Relativity, addressing coupling to a non-linear electromagnetic field, together with a negative cosmological constant, we obtain the general static spherical symmetric black hole solution with magnetic charges, which is asymptotic to anti-de Sitter (AdS) space-times. In particular, for a degenerate case the solution becomes a Hayward–AdS black hole, which is regular everywhere in the full space-time. The existence of such a regular black hole solution preserves the weak energy condition, while the strong energy condition is violated. We then derive the first law and the Smarr formula of the black hole solution. We further discuss its thermodynamic properties and study the critical phenomena in the extended phase space where the cosmological constant is treated as a thermodynamic variable as well as the parameter associated with the non-linear electrodynamics. We obtain many interesting results such as: the Maxwell equal area law in the
P
-
V
(or
S
-
T
) diagram is violated and consequently the critical point
(
T
∗
,
P
∗
)
of the first order small–large black hole transition does not coincide with the inflection point (
T
c
,
P
c
) of the isotherms; the Clapeyron equation describing the coexistence curve of the Van der Waals (vdW) fluid is no longer valid; the heat capacity at constant pressure is finite at the critical point; the various exponents near the critical point are also different from those of the vdW fluid.
Journal Article
On the Noether charge and the gravity duals of quantum complexity
A
bstract
The physical relevance of the thermodynamic volumes of AdS black holes to the gravity duals of quantum complexity was recently argued by Couch et al. In this paper, by generalizing the Wald-Iyer formalism, we derive a geometric expression for the thermodynamic volume and relate its product with the thermodynamic pressure to the non-derivative part of the gravitational action evaluated on the Wheeler-DeWitt patch. We propose that this action provides an alternative gravity dual of the quantum complexity of the boundary theory. We refer this to “complexity=action 2.0” (CA-2) duality. It is significantly different from the original “complexity=action” (CA) duality as well as the “complexity=volume 2.0” (CV-2) duality proposed by Couch et al. The latter postulates that the complexity is dual to the spacetime volume of the Wheeler-DeWitt patch. To distinguish our new conjecture from the various dualities in literature, we study a number of black holes in Einstein-Maxwell-Dilation theories. We find that for all these black holes, the CA duality generally does not respect the Lloyd bound whereas the CV-2 duality always does. For the CA-2 duality, although in many cases it is consistent with the Lloyd bound, we also find a counter example for which it violates the bound as well.
Journal Article
The growth of operator entropy in operator growth
A
bstract
We study upper bounds on the growth of operator entropy
S
K
in operator growth. Using uncertainty relation, we first prove a dispersion bound on the growth rate
|∂
t
S
K
| ≤
2
b
1
∆
S
K
, where
b
1
is the first Lanczos coefficient and ∆
S
K
is the variance of
S
K
. However, for irreversible process, this bound generally turns out to be too loose at long times. We further find a tighter bound in the long time limit using a universal logarithmic relation between Krylov complexity and operator entropy. The new bound describes the long time behavior of operator entropy very well for physically interesting cases, such as chaotic systems and integrable models.
Journal Article
Warm/cool-tone switchable thermochromic material for smart windows by orthogonally integrating properties of pillar6arene and ferrocene
Functional materials play a vital role in the fabrication of smart windows, which can provide a more comfortable indoor environment for humans to enjoy a better lifestyle. Traditional materials for smart windows tend to possess only a single functionality with the purpose of regulating the input of solar energy. However, different color tones also have great influences on human emotions. Herein, a strategy for orthogonal integration of different properties is proposed, namely the thermo-responsiveness of ethylene glycol-modified pillar[6]arene (
EGP6
) and the redox-induced reversible color switching of ferrocene/ferrocenium groups are orthogonally integrated into one system. This gives rise to a material with cooperative and non-interfering dual functions, featuring both thermochromism and warm/cool tone-switchability. Consequently, the obtained bifunctional material for fabricating smart windows can not only regulate the input of solar energy but also can provide a more comfortable color tone to improve the feelings and emotions of people in indoor environments.
Materials for smart windows usually possess single functionality, thus developing materials that regulate solar energy whilst changing color to affect human emotion is desirable. Here the authors combine pillar[6]arenes and ferrocene/ferrocenium groups to produce warm/cool tone-switchable thermochromic materials.
Journal Article
Black holes in vector-tensor theories and their thermodynamics
In this paper, we study Einstein gravity either minimally or non-minimally coupled to a vector field which breaks the gauge symmetry explicitly in general dimensions. We first consider a minimal theory which is simply the Einstein-Proca theory extended with a quartic self-interaction term for the vector field. We obtain its general static maximally symmetric black hole solution and study the thermodynamics using Wald formalism. The aspects of the solution are much like a Reissner-Nordstrøm black hole in spite of that a global charge cannot be defined for the vector. For non-minimal theories, we obtain a lot of exact black hole solutions, depending on the parameters of the theories. In particular, many of the solutions are general static and have maximal symmetry. However, there are some subtleties and ambiguities in the derivation of the first laws because the existence of an algebraic degree of freedom of the vector in general invalids the Wald entropy formula. The thermodynamics of these solutions deserves further studies.
Journal Article
Deep learning-based high-accuracy quantitation for lumbar intervertebral disc degeneration from MRI
To help doctors and patients evaluate lumbar intervertebral disc degeneration (IVDD) accurately and efficiently, we propose a segmentation network and a quantitation method for IVDD from T2MRI. A semantic segmentation network (BianqueNet) composed of three innovative modules achieves high-precision segmentation of IVDD-related regions. A quantitative method is used to calculate the signal intensity and geometric features of IVDD. Manual measurements have excellent agreement with automatic calculations, but the latter have better repeatability and efficiency. We investigate the relationship between IVDD parameters and demographic information (age, gender, position and IVDD grade) in a large population. Considering these parameters present strong correlation with IVDD grade, we establish a quantitative criterion for IVDD. This fully automated quantitation system for IVDD may provide more precise information for clinical practice, clinical trials, and mechanism investigation. It also would increase the number of patients that can be monitored.
Globally, as a major public health problem, low back pain has been the leading cause of disability worldwide for the past 30 years. Here, the authors propose a segmentation network and a quantitative method lumbar intervertebral disc degeneration assessment.
Journal Article
An Unexpected Synthesis of 2-Sulfonylquinolines via Deoxygenative C2-Sulfonylation of Quinoline N-Oxides with Sulfonyl Chlorides
A mild, efficient and practical protocol for the preparation of 2-sulfonylquinolines through CS2/Et2NH-induced deoxygenative C2-H sulfonylation of quinoline N-oxides with readily available RSO2Cl was developed. The reaction proceeded well under transition-metal-free conditions and exhibited a wide substrate scope and functional group tolerance. The preliminary studies suggested that the nucleophilic sulfonyl sources were generated in situ via the reaction of CS2, Et2NH and sulfonyl chlorides.
Journal Article
Analytical approach to criticality of AdS black holes
A
bstract
We establish a hidden symmetry between the specific volumes of the coexistent phases and hence develop an analytical approach to study criticality of AdS black holes. In particular, using the method, we solve the coexistence line exactly for a variety of black holes, including the charged AdS black hole in diverse dimensions, the rotating AdS black hole, the Gauss-Bonnet black hole and the quantum BTZ black hole as well as the Van der Waals fluid.
Journal Article
Bulk entanglement and its shape dependence
We study bulk entanglement entropy in even spacetime dimensions using the heat kernel method, which captures the universal piece of entanglement entropy, a logarithmically divergent term in even dimensions. In four dimensions, we perform explicit calculations for various shapes of boundary subregions. In particular, for a cusp subregion with an arbitrary opening angle, we find that the bulk entanglement entropy always encodes the same universal information about the boundary theories as the leading entanglement entropy in the large N limit, up to a fixed proportional constant. By smoothly deforming a circle in the boundary, we find that to leading order of the deformations, the bulk entanglement entropy shares the same shape dependence as the leading entanglement entropy and hence the same physical information can be extracted from both cases. This establishes an interesting local/nonlocal relation for holographic CFT3. However, the result does not hold for higher dimensional holographic theories.
Journal Article