arXiv subjects

Zhenhua Zhou

Publications and source records attributed to Zhenhua Zhou.

13 recordsLinked to original sources

arXiv2025

Mixer-Informer-Based Two-Stage Transfer Learning for Long-Sequence Load Forecasting in Newly Constructed Electric Vehicle Charging Stations

The rapid rise in electric vehicle (EV) adoption demands precise charging station load forecasting, challenged by long-sequence temporal dependencies and limited data in new facilities. This study proposes MIK-TST, a novel two-stage transfer learning framework integrating Mixer, Informer, and Kolmogorov-Arnold Networks (KAN). The Mixer fuses multi-source features, Informer captures long-range dependencies via ProbSparse attention, and KAN enhances nonlinear modeling with learnable activation functions. Pre-trained on extensive data and fine-tuned on limited target data, MIK-TST achieves 4% and 8% reductions in MAE and MSE, respectively, outperforming baselines on a dataset of 26 charging stations in Boulder, USA. This scalable solution enhances smart grid efficiency and supports sustainable EV infrastructure expansion.

eess.SY↗

arXiv2020

Holograhic two-currents model with coupling and its conductivites

We implement a holographic gravity model of two gauge fields with a coupling between them, which is dual to a two-currents model. An analytical black brane solution is obtained. In particular, we work out the expressions of conductivities with coupling and find that the expressions of conductivities are directly related to the coupling parameter $θ$. It is the main topic of our present work. As an application, we calculate the conductivities by the scheme outlined here and briefly discuss the properties of the conductivities. An interesting property is that as the coupling $θ$ increases, the dip at low frequency in $Re[σ_A]$/$Re[σ_B]$ becomes deepening and then turns into a hard-gap-like when $θ=1$, which is independent of the doping $χ$. Some monotonic behaviors of the conductivities are also discussed.

hep-th↗

arXiv2020

Doped holographic fermionic system

We construct a two-current model. It includes two gauge fields, which introduce the doping effect, and a neutral scalar field. And then we numerically construct an AdS black brane geometry with scalar hair. Over this background, we study the fermionic system with the pseudoscalar Yukawa coupling. Some universal properties from the pseudoscalar Yukawa coupling are revealed. In particular, as the coupling increases, there is a transfer of the spectral weight from the low energy band to the high energy band. The transfer is over low energy scales but not over all energy scales. The peculiar properties are also explored. The study shows that with the increase of the doping, the gap opens more difficult. It indicates that there is a competition between the pseudoscalar Yukawa coupling and the doping.

hep-th↗

arXiv2020

Particle motion and chaos

In this note, we consider particle falling in the black hole with an additional potential. Following the proposal by Susskind \cite{Susskind:2018tei}, we study the growth rate of the particle's Rindler momentum, which corresponds to the growth rate of the operator size in the dual chaotic system. A general analysis near the horizon shows that the growth rate of the particle's Rindler momentum of the particle falling with a regular potential is as the same as that of the particle free falling, which saturates the chaos bound. However, when the potential is singular, the growth rate is suppressed such that it is below the Lyapunov exponent. It implies that the chaos suppression may be captured by an additional singular potential in the gravity side. We further explicitly study a particle falling in hyperscaling violating spacetime to confirm the general analysis results. Finally we study the particle falling in AdS soliton geometry. It also exhibits a suppression of the growth of the Rindler momentum. It is attributed to that when the repulsive potential is introduced or the black hole horizon is absent, the particle is slowed down and its trajectory seen by a comoving observer is timelike, which corresponds a weak chaos system.

hep-th↗

arXiv2019

Holography of electrically and magnetically charged black branes

We construct a new class of black brane solutions in Einstein-Maxwell-dilaton (EMD) theory, which is characterized by two parameters $a,b$. Based on the obtained solutions, we make detailed analysis on the ground state in zero temperature limit and find that for many cases it exhibits the behavior of vanishing entropy density. We also find that the linear-T resistivity can be realized in a large region of temperature for the specific case of $a^2=1/3$, which is the Gubser-Rocha model dual to a ground state with vanishing entropy density. Moreover, for $a=1$ we analytically construct the black brane which is magnetically charged by virtue of the electric-magnetic (EM) duality. Various transport coefficients are calculated and their temperature dependence are obtained in the high temperature region.

hep-th↗

arXiv2018

Holographic transports from Born-Infeld electrodynamics with momentum dissipation

We construct the Einstein-axions AdS black hole from Born-Infeld electrodynamics. Various DC transport coefficients of the dual boundary theory are computed. The DC electric conductivity depends on the temperature, which is a novel property comparing to that in RN-AdS black hole. The DC electric conductivity are positive at zero temperature while the thermal conductivity vanishes, which implies that the dual system is an electrical metal but thermal insulator. The effects of Born-Infeld parameter on the transport coefficients are analyzed. Finally, we study the AC electric conductivity from Born-Infeld electrodynamics with momentum dissipation. For weak momentum dissipation, the low frequency behavior satisfies the standard Drude formula and the electric transport is coherent for various correction parameter. While for stronger momentum dissipation, the modified Drude formula is applied and we observe a crossover from coherent to incoherent phase. Moreover, the Born-Infeld correction amplifies the incoherent behavior. Finally, we study the non-linear conductivity in probe limit and compare our results with those observed in (i)DBI model.

hep-th↗

arXiv2018

The Lifshitz black branes and DC transport coefficients in massive Einstein-Maxwell-dilaton gravity

We construct analytical Lifshitz massive black brane solutions in massive Einstein-Maxwell-dilaton gravity theory. We also study the thermodynamics of these black brane solutions and obtain the thermodynamical stability conditions. On the dual nonrelativistic boundary field theory with Lifshitz symmetry, we analytically compute the DC transport coefficients, including the electric conductivity, thermoelectric conductivity, and thermal conductivity. The novel property of our model is that the massive term supports the Lifshitz black brane solutions with $z\neq 1$ in such a way that the DC transport coefficients in the dual field theory are finite. We also find that the Wiedemann-Franz law in this dual boundary field theory is violated, which indicates that it may involve strong interactions.

hep-th↗

arXiv2017

Holographic Metal-Insulator Transition in Higher Derivative Gravity

We introduce a Weyl term into the Einstein-Maxwell-Axion theory in four dimensional spacetime. Up to the first order of the Weyl coupling parameter $γ$, we construct charged black brane solutions without translational invariance in a perturbative manner. Among all the holographic frameworks involving higher derivative gravity, we are the first to obtain metal-insulator transitions (MIT) when varying the system parameters at zero temperature. Furthermore, we study the holographic entanglement entropy (HEE) of strip geometry in this model and find that the second order derivative of HEE with respect to the axion parameter exhibits maximization behavior near quantum critical points (QCPs) of MIT. It testifies the conjecture in 1502.03661 and 1604.04857 that HEE itself or its derivatives can be used to diagnose quantum phase transition (QPT).

hep-th↗

arXiv2016

Holographic incoherent transport in Einstein-Maxwell-dilaton Gravity

Recent progress in the holographic approach makes it more transparent that each conductivity can be decomposed into the coherent contribution due to momentum relaxation and the incoherent contribution due to intrinsic current relaxation. In this paper we investigate this decomposition in the framework of Einstein-Maxwell-dilaton theory. We derive the perturbation equations, which are decoupled for a large class of background solutions, and then obtain the analytic results of conductivity with the slow momentum relaxation in low frequency approximation, which is consistent with the known results from memory matrix techniques.

hep-th↗

arXiv2016

Holographic Shear Viscosity in Hyperscaling Violating Theories without Translational Invariance

In this paper we investigate the ratio of shear viscosity to entropy density, $η/s$, in hyperscaling violating geometry with lattice structure. We show that the scaling relation with hyperscaling violation gives a strong constraint to the mass of graviton and usually leads to a power law of temperature, $η/s\sim T^κ$. We find the exponent $κ$ can be greater than two such that the new bound for viscosity raised in arXiv:1601.02757 is violated. Our above observation is testified by constructing specific solutions with UV completion in various holographic models. Finally, we compare the boundedness of $κ$ with the behavior of entanglement entropy and conjecture a relation between them.

hep-th↗

arXiv2016

Power Law of Shear Viscosity in Einstein-Maxwell-Dilaton-Axion model

We construct charged black hole solutions with hyperscaling violation in the infrared(IR) region in Einstein-Maxwell-Dilaton-Axion theory and investigate the temperature behavior of the ratio of holographic shear viscosity to the entropy density. When translational symmetry breaking is relevant in the IR, the power law of the ratio is testified numerically at low temperature $T$, namely, $η/s\sim T^κ$, where the values of exponent $κ$ coincide with the analytical results. We also find that the exponent $κ$ is not affected by irrelevant current, but is reduced by the relevant current.

hep-th↗

arXiv2015

DC and Hall conductivity in holographic massive Einstein-Maxwell-Dilaton gravity

We investigate the holographic DC and Hall conductivity in massive Einstein-Maxwell-Dilaton (EMD) gravity. Two special EMD backgrounds are considered explicitly. One is dyonic Reissner-Nordstr$\ddot{o}$m-AdS (RN-AdS) geometry and the other one is hyperscaling violation AdS (HV-AdS) geometry. We find that the linear-T resistivity and quadratic-T inverse Hall angle can be simultaneously achieved in HV-AdS models, providing a hint to construct holographic models confronting with the experimental data of strange metal in future.

hep-th↗

arXiv2013

Action principle for the connection dynamics of scalar-tensor theories

A first-order action for scalar-tensor theories of gravity is proposed. The Hamiltonian analysis of the action gives the desired connection dynamical formalism, which was derived from the geometrical dynamics by canonical transformations. It is shown that this connection formalism in Jordan frame is equivalent to the alternative connection formalism in Einstein frame. Therefore, the action principle underlying loop quantum scalar-tensor theories is recovered.

gr-qc↗