We present a general procedure for constructing exact black hole solutions with electric or magnetic charges in general relativity coupled to a nonlinear electrodynamics. We obtain a variety of ...two-parameter family spherically symmetric black hole solutions. In particular, the singularity at the center of the space-time can be canceled in the parameter space and the black hole solutions become regular everywhere in space-time. We study the global properties of the solutions and derive the first law of thermodynamics. We also generalize the procedure to include a cosmological constant and construct regular black hole solutions that are asymptotic to anti–de Sitter space-time.
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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.
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.
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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.
Zero-dimensional (0D) halides perovskites, in which anionic metal-halide octahedra (MX 6 ) 4− are separated by organic or inorganic countercations, have recently shown promise as excellent ...luminescent materials. However, the origin of the photoluminescence (PL) and, in particular, the different photophysical properties in hybrid organic–inorganic and all inorganic halides are still poorly understood. In this work, first-principles calculations were performed to study the excitons and intrinsic defects in 0D hybrid organic–inorganic halides (C 4 N 2 H 14 X) 4 SnX 6 (X = Br, I), which exhibit a high photoluminescence quantum efficiency (PLQE) at room temperature (RT), and also in the 0D inorganic halide Cs 4 PbBr 6 , which suffers from strong thermal quenching when T > 100 K. We show that the excitons in all three 0D halides are strongly bound and cannot be detrapped or dissociated at RT, which leads to immobile excitons in (C 4 N 2 H 14 X) 4 SnX 6 . However, the excitons in Cs 4 PbBr 6 can still migrate by tunneling, enabled by the resonant transfer of excitation energy (Dexter energy transfer). The exciton migration in Cs 4 PbBr 6 leads to a higher probability of trapping and nonradiative recombination at the intrinsic defects. We show that a large Stokes shift and the negligible electronic coupling between luminescent centers are important for suppressing exciton migration; thereby, enhancing the photoluminescence quantum efficiency. Our results also suggest that the frequently observed bright green emission in Cs 4 PbBr 6 is not due to the exciton or defect-induced emission in Cs 4 PbBr 6 but rather the result of exciton emission from CsPbBr 3 inclusions trapped in Cs 4 PbBr 6 .
Lipids are a major component of food and important structural and functional constituents of cells in biological systems. However, this diverse group of substances is prone to oxidation through ...various pathways. Their oxidative stability depends on a number of intrinsic and extrinsic factors, including the unsaturation of their fatty acids, composition of minor components, environment conditions, delivery techniques and use of antioxidants, among others. Lipid oxidation has detrimental effects on both food quality and human health, and efforts must be made to minimize oxidation and improve oxidative stability of lipid products. Antioxidant strategy has been successfully employed in the food industry for quality preservation of the food products and in the medicinal industry for risk reduction of numerous oxidative stress-mediated diseases. This
tutorial review
will provide important knowledge about lipid oxidation, including the mechanism and factors involved in oxidation, as well as strategies for improving oxidative stability of lipids.
This tutorial review provides the latest information about lipid oxidation, including the mechanisms and factors involved, as well as strategies for improving oxidative stability of lipids.
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 pillar6arene (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.
In order to better improve the teaching quality of university teachers, an effective method should be adopted for evaluation and analysis. This work studied the machine learning algorithms and ...selected the support vector machine (SVM) algorithm to evaluate teaching quality. First, the principles of selecting evaluation indexes were briefly introduced, and 16 evaluation indexes were selected from different aspects. Then, the SVM algorithm was used for evaluation. A genetic algorithm (GA)-SVM algorithm was designed and experimentally analyzed. It was found that the training time and testing time of the GA-SVM algorithm were 23.21 and 7.25 ms, both of which were shorter than the SVM algorithm. In the evaluation of teaching quality, the evaluation value of the GA-SVM algorithm was closer to the actual value, indicating that the evaluation result was more accurate. The average accuracy of the GA-SVM algorithm was 11.64% higher than that of the SVM algorithm (98.36 vs 86.72%). The experimental results verify that the GA-SVM algorithm can have a good application in evaluating and analyzing teaching quality in universities with its advantages in efficiency and accuracy.
► Lipophilic ester derivatives of EGCG were prepared. ► The EGCG derivatives exhibited antioxidant activity in food model systems. ► The EGCG derivatives exhibited antioxidant activity in biological ...model systems. ► The EGCG derivatives may potentially be used in food and health application areas.
Epigallocatechin gallate (EGCG) was structurally modified for enhanced lipophilicity and hence expanded applications, as well as improved cellular absorption in vivo. Ester derivatives of EGCG with stearic acid, eicosapentaenoic acid and docosahexaenoic acid were prepared. All EGCG derivatives inhibited oxidation of bulk oil, and their potency was superior or similar to that of the parent EGCG molecule. The derivatives were more efficient than EGCG in inhibiting oxidation in a β-carotene/linoleic acid emulsion and pork model systems, and their efficiency correlated well with their lipophilicity. In biological systems, the ester derivatives showed higher cell membrane affinity and therefore better cellular absorption than EGCG. The derivatives were more effective than EGCG against Cu2+-induced LDL-cholesterol oxidation and also effectively inhibited hydroxyl and peroxyl radical-induced DNA scission and UV-induced liposome oxidation. These results suggest that EGCG esters may be used in food as lipophilic alternatives to EGCG, without compromising functional and physiological properties. Moreover, EGCG–polyunsaturated fatty acid esters may render additional advantages to human health.
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