arXiv subjects

Wenhe Cai

Publications and source records attributed to Wenhe Cai.

15 recordsLinked to original sources

arXiv2026

Analytic Computation of Dilaton Black Hole Quasinormal Modes via Seiberg-Witten Theory

We study the quasinormal modes (QNMs) of dilaton black holes in Einstein-Maxwell-dilaton gravity through a correspondence with the quantum Seiberg-Witten (SW) curve of $\mathcal{N}=2$ SU(2) gauge theory with $N_f=3$ hypermultiplets. By mapping both the black hole perturbation equation and the quantum SW curve to the confluent Heun form, the QNM problem is reformulated in a gauge-theoretic framework, and the spectrum is obtained via the SW quantization condition. The resulting frequencies show excellent agreement with those computed using the WKB and continued fraction methods, with typical deviations below $10^{-3}$. The QNM spectrum exhibits consistent trends: increasing the black hole charge or scalar field mass raises the oscillation frequency, while higher angular momentum reduces the damping rate. These results demonstrate the precision of the quantum SW framework in describing black hole perturbations and reveal new links between supersymmetric gauge theories and gravitational dynamics.

hep-th↗

arXiv2025

Off-diagonal coupling of supersymmetric SYK model

In this work, we consider the off-diagonal coupling between two supersymmetric SYK models, which preserves both supersymmetry and solvability. We found that the interaction terms of the $N=2$ supersymmetric SYK have a holographic interpretation as a possible supersymmetric traversable wormhole. First we introduce the coupling in the trivial Homologic $N=1$ SYK model as a simplified example. Similar couplings can be implied in $N=2$ chiral SYK model with BPS states. We propose a special form of $N=4$ SYK by introducing supermultiplets, and which also naturally include the coupling terms. The holographic picture of $N=4$ SYK does not have an eternal solution in the low energy limit. And the effective actions are studied in both thermal limit and low energy limit. We also investigate the SYK-like thermal field double states of the supersymmetric SYK and the transmission amplitude between single-side $N=2$ models in Lorentz time. Additionally, the multi-side $N=2,4$ OTOCs are also studied.

hep-th↗

arXiv2024

$T\bar{T}$ deformation on non-Hermitian two coupled SYK model

We investigate $T\bar{T}$ deformation on non-Hermitian coupled Sachdev-Ye-Kitaev (SYK) model and the holographic picture. The relationship between ground state and thermofield double state is preserved under the $T\bar{T}$ deformation. We prove that $T\bar{T}$ deformed theory provides a reparameterization in large $N$ limit. These deformation effects is calculated numerically with green functions and free energy. The thermodynamic phase structures show the equivalence of the wormhole-black hole picture between non-Hermitian model and Hermitian model still holds under $T\bar{T}$ deformation. We also study the correlation function in Lorentz time and revival dynamic.

hep-th↗

arXiv2024

Doped Holographic Superconductors in Gubser-Rocha model

We construct a doped holographic superconductor in the Gubser-Rocha model, and realize a superconducting dome in the middle of the temperature-doping phase diagram. It is worth noting that unlike the previous researches, the profile of our dome shrinks inward near zero temperature. From the numerical observation for the coupling dependence of the phase diagram, we find that the coupling between the two gauge fields plays a crucial role in the formation of dome. We also analytically calculate the DC conductivity of the normal phase of the system in the momentum dissipation and obtain the resistivity which is proportional to temperature. The AC conductivity is calculated numerically.

hep-th↗

arXiv2022

Non-Hermitian quantum system generated from two coupled Sachdev-Ye-Kitaev models

We show that a non-Hermitian two coupled Sachdev-Ye-Kitaev (SYK) model can provide thermodynamic structure equivalent to Hermitian two coupled SYK model. The energy spectrum, the entanglement degree of the ground states and the low energy effective action of this model are not influenced by the non-Hermiticity. The novel biorthogonal ground states demonstrates that two SYK sites, one of which can be in the ground state and the other in the Schwarzian excited state by tuning the non-Hermiticity. We find evidence that the free energy is independent of the non-Hermiticity.

hep-th↗

arXiv2022

Heun's equation and analytic structure of the Gap in Holographic superconductivity

We present the new method to calculate the critical temperature as a function of $Δ$, conformal dimension of the cooper operator. We find that, in the regime $1/2\leq Δ<1$ where the AC conductivity does not show a gap, the critical temperature is not well defined. We also got expression of AC conductivity for $Δ=2$, which agrees with numerical result in the probe approximation.

hep-th↗

arXiv2021

The superconducting dome for holographic doped Mott insulator with hyperscaling violation

We reconsider the holographic model featuring a superconducting dome on the temperature-doping phase diagram with a modified view on the role of the two charges. The first type charge with density $ρ_{A}$ make the Mott insulator, and the second one with $ρ_{B}$ is the extra charge by doping, so that the complex scalar describing the cooper pair condensation couples only with the second charge. We point out that the key role in creating the dome is played by the three point interaction $-c χ^{2} F_{μν}G^{μν}$. The $Tc$ increases with their coupling. We also consider the effect of the quantum critical point hidden under the dome using the geometry of hyperscaling violation. Our results show that the dome size and optimal temperature increase with $z$ whatever is $θ$, while we get bigger $θ$ for larger (smaller) dome depending on $z>2$ ($z<2$). We also point out that the condensate increases for bigger value of $θ$ but for smaller value of $z$.

hep-th↗

arXiv2021

Superconducting gap ratio from strange metal phase in the absence of quasiparticles

A lattice model for strongly interacting electrons motivated by a rank-3 tensor model provides a tool for understanding the pairing mechanism of high-temperature superconductivity. This SYK-like model describes the strange metal phase in the cuprate high temperature superconductors. Our calculation indicates that the superconducting gap ratio in this model is higher than the ratio in the BCS theory due to the coupling term and the spin operator. Under certain conditions, the ratio also agrees with the BCS theory. Our results relate to the case of strong coupling, so it may pave the way to gaining insight into the cuprate high temperature superconductors.

cond-mat.str-el↗

arXiv2019

Sound modes and stability of momentum dissipated black branes in holography

We systematically investigate the sound modes of momentum dissipated holographic systems. In particular, we focus on the Einstein-linear axions and the Einstein-Maxwell-dilaton-axion theories in four-dimensional bulk spacetime dimensions. The sound velocities of the two theories are computed respectively and the sound attenuation of the Einstein-Maxwell-axion theory is also calculated analytically. We also obtain numeral dispersion relations in the two theories which match with our analytical results. Our results show that the sound velocity of the Einstein-Maxwell-dilaton theory with additional linear axion fields is equivalent to that of 2 + 1 - dimensional Banados-Teitelboim-Zanelli black holes. It allowed us to compare our solution of the Einstein-linear axions theory with that of systems without translational invariance from another method. After the computation on the sound velocity, we calculate the quasinormal modes of scalar-type fluctuations in the Einstein-Maxwell-dilaton-axion theory. The results show that a dynamical instability is observed under the condition that the null energy condition is violated.

hep-th↗

arXiv2019

Electromagnetic instability and Schwinger effect in the Witten-Sakai-Sugimoto model with D0-D4 background

Using the Witten-Sakai-Sugimoto model in the D0-D4 background, we holographically compute the vacuum decay rate of the Schwinger effect in this model. Our calculation contains the influence of the D0-brane density which could be identified as the $θ$ angle or chiral potential in QCD. Under the strong electromagnetic fields, the instability appears due to the creation of quark-antiquark pairs and the associated decay rate can be obtained by evaluating the imaginary part of the effective Euler-Heisenberg action which is identified as the action of the probe brane with a constant electromagnetic field. In the bubble D0-D4 configuration, we find the decay rate decreases when the $θ$ angle increases since the vacuum becomes heavier in the present of the glue condensate in this system. And the decay rate matches to the result in the black D0-D4 configuration at zero temperature limit according to our calculations. In this sense, the Hawking-Page transition of this model could be consistently interpreted as the confined/deconfined phase transition. Additionally there is another instability from the D0-brane itself in this system and we suggest that this instability reflects to the vacuum decay triggered by the $θ$ angle as it is known in the $θ$-dependent QCD.

hep-th↗

arXiv2018

Holographic three flavor baryon in the Witten-Sakai-Sugimoto model with the D0-D4 background

With the construction of the Witten-Sakai-Sugimoto model in the D0-D4 background, we systematically investigate the holographic baryon spectrum in the case of three flavors. The background geometry in this model is holographically dual to $U\left(N_{c}\right)$ Yang-Mills theory in large $N_{c}$ limit involving an excited state with a nonzero $θ$ angle or glue condensate $\left\langle \mathrm{Tr}\mathcal{F}\wedge\mathcal{F}\right\rangle =8π^{2}N_{c}\tildeκ$, which is proportional to the charge density of the smeared D0-branes through a parameter $b$ or $\tildeκ$. The classical solution of baryon in this model can be modified by embedding the Belavin-Polyakov-Schwarz-Tyupkin (BPST) instanton and we carry out the quantization of the collective modes with this solution. Then we extend the analysis to include the heavy flavor and find that the heavy meson is always bound in the form of the zero mode of the flavor instanton in strong coupling limit. The mass spectrum of heavy-light baryons in the situation with single- and double-heavy baryon is derived by solving the eigen equation of the quantized collective Hamiltonian. Afterwards we obtain that the constraint of stable baryon states has to be $1<b<3$ and the difference in the baryon spectrum becomes smaller as the D0 charge increases. It indicates that quarks or mesons can not form stable baryons if the $θ$ angle or glue condensate is sufficiently large. Our work is an extension of the previous study of this model and also agrees with those conclusions.

hep-th↗

arXiv2018

Diffusion in higher dimensional SYK model with complex fermions

We construct a new higher dimensional SYK model with complex fermions on bipartite lattices. As an extension of the original zero-dimensional SYK model, we focus on the one-dimension case, and similar Hamiltonian can be obtained in higher dimensions. This model has a conserved U(1) fermion number Q and a conjugate chemical potential μ. We evaluate the thermal and charge diffusion constants via large q expansion at low temperature limit. The results show that the diffusivity depends on the ratio of free Majorana fermions to Majorana fermions with SYK interactions. The transport properties and the butterfly velocity are accordingly calculated at low temperature. The specific heat and the thermal conductivity are proportional to the temperature. The electrical resistivity also has a linear temperature dependence term.

hep-th↗

arXiv2016

Sound waves in the compactified D0-D4 brane system

As an extension to our previous work, we study the transport properties of the Witten-Sakai-Sugimoto model in the black D4-brane background with smeared D0-branes (D0-D4/D8 system). Because of the presence of the D0-branes, in the bubble configuration this model is holographically dual to 4d QCD or Yang-Mills theory with a Chern-Simons term. And the number density of the D0-branes corresponds to the coupling constant ($θ$ angle) of the Chern-Simons term in the dual field theory. In this paper, we accordingly focus on small number density of the D0-branes to study the sound mode in the black D0-D4 brane system since the coupling of the Chern-Simons term should be quite weak in QCD. Then we derive its 5d effective theory and analytically compute the speed of sound and the sound wave attenuation in the approach of Gauge/Gravity duality. Our result shows the speed of sound and the sound wave attenuation is modified by the presence of the D0-branes. Thus they depend on the $θ$ angle or chiral potential in this holographic description.

hep-th↗

arXiv2014

On the Elliptic Genus of Three E-strings and Heterotic Strings

A precise formula for the elliptic genus of three E-strings is presented. The related refined free energy coincides with the result calculated from topological string on local half K3 Calabi-Yau threefold up to genus twelve. The elliptic genus of three heterotic strings computed from M9 domain walls matches with the result from orbifold formula to high orders. This confirms the n=3 case of the recent conjecture that n pairs of E-strings can recombine into n heterotic strings.

hep-th↗

arXiv2014

Baryons in the Sakai-Sugimoto model in the D0-D4 background

The baryon spectrum in the Sakai-Sugimoto model in the D4 background with smeared D0 charges is studied. We follow the instanton description of baryons by Hata et al.[Prog. Theor. Phys. 117, 1157]. The background corresponds to an excited state with nonzero glue condensate $\langle {\rm tr} (F_{μν}\tilde F^{μν})\rangle$ which is proportional to the D0 charge density. The baryon size shrinks when we turn on small D0 charge density. But for larger D0 charge density where massive modes in the gauge theory may also take effect, the size of baryons will grow. The difference between baryon masses will become smaller when D0 charge density increases. There may also be indications that the baryon will become unstable and cannot exist for sufficiently large D0 density.

hep-th↗