Searcharxiv⌕ Search

arXiv subjects

Haitang Yang

Publications and source records attributed to Haitang Yang.

At least 19 recordsLinked to original sources
arXiv2026

Exact and Finite de Sitter QFT from CFT

Parallel to the AdS Scale-Space construction in \cite{Yang:2026AdS}, we construct a $(d+1)$-dimensional de Sitter QFT directly from $d$-dimensional CFT data. The dS geometry is the moduli space of oriented balls, and the lifted operators are obtained by conformal-family Casimir completion. The Euclidean parent CFT gives a finite wavefunction representation, while the Minkowski parent CFT gives a double-time representation that is unitary in the parent-time polarization. This provides a CFT-based framework for reexamining puzzles of dS and double-time QFT.

hep-th↗
arXiv2026

Exact Holographic Kinematics in AdS/CFT

We propose that holography contains an exact kinematic sector distinct from holographic dynamics. The appropriate setting for this sector is a CFT on an open solid torus in the Weyl frame. The open solid torus introduces an intrinsic scale, and the Weyl frame makes this scale manifest as an extra bulk direction. The resulting bulk-boundary pairs are exact and finite: no cutoff, large-$N$ limit, strong-coupling assumption, or heavy-operator approximation is required. The AdS geometry appearing in this sector should be understood as a kinematic geometry; only in special CFTs and appropriate limits is it promoted to a dynamical semiclassical bulk. The standard boundary-anchored dictionary entries are recovered only as singular limits. As a striking demonstration, we show that Weyl-frame two-point functions provide a replica-free definition of entanglement entropy.

hep-th↗
arXiv2026

Exact Bulk-Boundary Pairs in AdS/CFT

We show that for a CFT$_D$ on a flat open solid torus, the two point function in the Weyl frame is exactly paired with a finite geodesic lying entirely in the AdS$_{D+1}$ bulk interior. This relation is exact and requires neither large $N$, strong coupling, nor heavy operators. The exactness is that of conformal kinematics; no semiclassical bulk dynamics is assumed. The standard boundary-anchored relation is a singular limit of the exact pair. For the free scalar, a mode expansion along $S^1$ generates an infinite tower of effective masses on $H_{D-1}$, whose intricate propagators resum exactly to the same simple higher-dimensional geodesic expression. Together with another exact pair between disjoint entanglement entropy and entanglement wedge cross-section found on the same open solid torus, this result points toward a broader exact-pair program in AdS/CFT.

hep-th↗
arXiv2026

Early-Time Nonlinear Growth in an Unstable Q-Ball Hairy Black Hole

Early-time evolution away from an unstable equilibrium in a nonlinear system is often expected to be governed by the associated linear instability. Combining full nonlinear evolution with first- and second-order quasinormal mode (QNM) calculations, we show that this expectation can fail during the unstable growth stage of a Q-ball hairy black hole in Einstein-Maxwell theory with a charged self-interacting scalar field. The linear unstable QNM has a much larger amplitude in one component of the scalar field than in the other: the more strongly responding component follows that mode, whereas the early growth of the more weakly responding component is dominated by a second-order QNM sourced by the linear unstable mode. This occurs while the evolution remains perturbative. Our results thus show that the early growth of an individual component need not be governed by its linear response.

gr-qc↗
arXiv2025

Spin-induced Scalarized Black Holes in Einstein-Maxwell-scalar Models

We construct spin-induced scalarized black hole solutions in a class of Einstein-Maxwell-scalar models, where a scalar field is non-minimally coupled to the electromagnetic field. Our results show that scalar hair develops only for rapidly rotating black holes, while slowly spinning ones remain well described by the Kerr-Newman (KN) metric. The scalar field contributes only a small fraction of the total mass, indicating suppressed nonlinear effects. This suppression may account for the narrow existence domains of scalarized black holes and the similarities observed in their existence domains across different coupling functions. Moreover, scalarized black holes are found to coexist with linearly stable, entropically favored KN black holes. These results motivate further investigations into the nonlinear dynamics and stability of scalarized black holes in these models.

gr-qc↗
arXiv2025

Timelike entanglement entropy Revisited

We present an operator-algebraic definition for timelike entanglement entropy in QFT under a few mild postulates. This rigorously defined timelike entanglement entropy is real-valued due to the timelike tube theorem. We further demonstrate why the timelike entanglement entropy should be real-valued from both path integral argument and holography perspective.

hep-th↗
arXiv2025

Entanglement Entropy of Mixed State in Thermal CFT$_2$

Using the subtraction approach, we give the bipartite mixed state entanglement entropy in thermal $\text{CFT}_2$. With these entanglement entropies, we examine in detail the holographic duals of different entangling configurations unambiguously. In the thermofield double state, we show a horizon-crossing feature in two-sided entanglement configuration.

hep-th↗
arXiv2025

Mixed State Entanglement Entropy in CFT

How to calculate the entanglement entropy between two subsystems for a mixed state has remained an important problem. In this paper, we provide a straightforward method, namely the subtraction approach, to solve this problem for generic covariant bipartite mixed states, where time dependence is explicitly included. We further demonstrate that the mixed state entanglement entropy $S_\text{vN}$ can be calculated in a more abstract yet powerful way. Within the context of the AdS$_3$/CFT$_2$ and a configuration of AdS$_5$/CFT$_4$ correspondences, we show that $S_\text{vN}$ exactly matches the corresponding entanglement wedge cross section in the AdS bulk, respectively.

hep-th↗
arXiv2024

Realization of "ER=EPR"

We provide a concrete and computable realization of the $ER=EPR$ conjecture, by deriving the Einstein-Rosen bridge from the quantum entanglement in the thermofield double CFT. The Bekenstein-Hawking entropy of the wormhole is explicitly identified as an entanglement entropy between subsystems of the thermofield double state. Furthermore, our results provide a quantitative verification of Van Raamsdonk's conjecture about spacetime emergence.

hep-th↗
arXiv2024

How Einstein's Equation Emerges From CFT$_2$

The {\it finiteness} of the entanglement entropies between disjoint subsystems enables us to show that, the dynamical equation of the entanglement entropy in CFT$_2$ is precisely three dimensional Einstein's equation. We establish a profound relation between the cosmological constant and CFT$_2$ entanglement entropy. Thus entanglement entropies induce internal gravitational geometries in CFT$_2$. Extracting the dual metric from an entanglement entropy becomes a straightforward procedure. Remarkably, we discover that the renormalization group equation is a geometric identity.

hep-th↗
arXiv2024

Observational Signatures of Traversable Wormholes

In this paper, we study the observational signatures of traversable Simpson-Visser wormholes illuminated by luminous celestial spheres and orbiting hot spots. We demonstrate that when light sources and observers are on the same side of the wormholes, the images of the wormholes mimic those of black holes. However, when the light sources are positioned on the opposite side from observers, photons traversing the wormhole throat generate distinct observational signatures. Specifically, unlike black hole images, the wormhole images are confined within the critical curve, resulting in smaller centroid variations. Furthermore, the light curve of hot spots can exhibit additional peaks.

gr-qc↗
arXiv2024

Polarized Image of a Synchrotron-emitting Ring in Einstein-Maxwell-scalar Theory

This study investigates polarized images of an equatorial synchrotron-emitting ring surrounding hairy black holes within the Einstein-Maxwell-scalar theory. Our analysis demonstrates qualitative similarities between the polarization patterns of hairy black holes and Schwarzschild black holes. However, due to the non-minimal coupling between the scalar and electromagnetic fields, an increase in black hole charge and coupling constant can substantially amplify polarization intensity and induce deviations in the electric vector position angle. These effects may offer observational signatures to distinguish hairy black holes from Schwarzschild black holes.

gr-qc↗
arXiv2024

Spin-induced Scalar Clouds around Kerr-Newman Black Holes

Recent studies have demonstrated that a scalar field non-minimally coupled to the electromagnetic field can experience a spin-induced tachyonic instability near Kerr-Newman black holes, potentially driving the formation of scalar clouds. In this paper, we construct such scalar clouds for both fundamental and excited modes, detailing their existence domains and wave functions. Our results indicate that a sufficiently strong coupling between the scalar and electromagnetic fields is essential for sustaining scalar clouds. Within the strong coupling regime, black holes that rotate either too slowly or too rapidly are unable to support scalar clouds. Furthermore, we observe that scalar cloud wave functions are concentrated near the black hole's poles. These findings provide a foundation for future investigations of spin-induced scalarized Kerr-Newman black holes.

gr-qc↗
arXiv2024

String Scattering and Evolution of Ryu-Takayanagi Surface

In this paper, our aim is to illustrate that the process of open string scattering corresponds to the evolution of the entanglement wedge, where the scattering distance is identified as the entanglement wedge cross section. Moreover, open-closed string scattering, specifically the disk-disk interaction, works for the evolution of the reflected entanglement wedge, with the circumference of the waist cross section equating to the reflected entropy. It therefore provides evidence for the deep connections between the string worldsheet and the Ryu-Takayanagi surface. This connection is not only a coincidence rooted in hyperbolic geometry; it also reflects an additional correspondence between two distinct theories: mutual information and the geometric BV master equation.

hep-th↗
arXiv2024

Stationary Scalar Clouds around Kerr-Newman Black Holes

This study investigates scalar clouds around Kerr-Newman black holes within the Einstein-Maxwell-scalar model. Tachyonic instabilities are identified as the driving mechanism for scalar cloud formation. Employing the spectral method, we numerically compute wave functions and parameter space existence domains for both fundamental and excited scalar cloud modes. Our analysis demonstrates that black hole spin imposes an upper limit on the existence of scalar clouds, with excited modes requiring stronger tachyonic instabilities for their formation. These findings lay the groundwork for exploring the nonlinear dynamics and astrophysical implications of scalar clouds.

gr-qc↗
arXiv2024

Electrical Impedance Tomography Based Closed-loop Tumor Treating Fields in Dynamic Lung Tumors

Tumor Treating Fields (TTFields) is a non-invasive anticancer modality that utilizes alternating electric fields to disrupt cancer cell division and growth. While generally well-tolerated with minimal side effects, traditional TTFields therapy for lung tumors faces challenges due to the influence of respiratory motion. We design a novel closed-loop TTFields strategy for lung tumors by incorporating electrical impedance tomography (EIT) for real-time respiratory phase monitoring and dynamic parameter adjustments. Furthermore, we conduct theoretical analysis to evaluate the performance of the proposed method using the lung motion model. Compared to conventional TTFields settings, we observed that variations in the electrical conductivity of lung during different respiratory phases led to a decrease in the average electric field intensity within lung tumors, transitioning from end-expiratory (1.08 V/cm) to end-inspiratory (0.87 V/cm) phases. Utilizing our proposed closed-Loop TTFields approach at the same dose setting (2400 mA, consistent with the traditional TTFields setting), we can achieve a higher and consistent average electric field strength at the tumor site (1.30 V/cm) across different respiratory stages. Our proposed closed-loop TTFields method has the potential to improved lung tumor therapy by mitigating the impact of respiratory motion.

physics.med-ph↗