arXiv subjects

Yu-Qi Chen

Publications and source records attributed to Yu-Qi Chen.

At least 19 recordsLinked to original sources

arXiv2026

Rotating Black Holes and the Kerr/CFT Correspondence in Einstein-Bumblebee Gravity

We constructed rotating black holes with equal angular momentum in five dimensional Einstein-Bumblebee gravity with and without cosmological constant. Their thermodynamic properties are examined via two distinct methods: the Wald formalism and the Komar integral. Notably, the conserved charges, including mass, angular momentum, and entropy, computed from these two approaches differ by a constant prefactor that is solely determined by the Bumblebee coupling. Subsequently, we apply the Kerr/CFT correspondence to derive the microscopic entropy of these black holes and find that it precisely reproduces the entropy in Komar-integral version, rather than the Wald entropy.

gr-qc↗

arXiv2025

Non-Hermitian edge burst of sound

Non-Hermitian band topology can give rise to phenomena with no counterparts in Hermitian systems. A well-known example is the non-Hermitian skin effect (NHSE), where Bloch eigenstates localize at a boundary, induced by a nontrivial spectrum winding number. In contrast, recent studies on lossy non-Hermitian lattices have uncovered an unexpected boundary-localized loss probability-a phenomenon that requires not only non-Hermitian band topology but also the closure of the imaginary (dissipative) gap. Here, we demonstrate the non-Hermitian edge burst in a classical-wave metamaterial: a lossy nonreciprocal acoustic crystal. We show that, when the imaginary gap remains closed, edge bursts can occur at the right boundary, left boundary, or both boundaries simultaneously, all under the same non-Hermitian band topology; the latter scenario is known as a bipolar edge burst. The occurrence of each scenario depends on the number and location of the imaginary gap closure points in the eigenenergy spectra. These findings generalize the concept of edge burst from quantum to classical wave systems, establish it as an intrinsic material property, and enrich the physics of the complex interplay between non-Hermitian band topology and other physical properties in non-Hermitian systems.

cond-mat.mes-hall↗

arXiv2025

Taub-NUT-like Black Holes in Einstein-Bumblebee Gravity

We consider Einstein-Bumblebee gravity and construct a novel Taub-NUT-like black hole solution within this theory. Different from the Taub-NUT black hole in Einstein gravity (which is Ricci-flat), our newly constructed Taub-NUT-like black hole is not Ricci-flat. Armed with the Wald formalism, we extensively study the thermodynamics of this black hole solution and confirm that both the first law of thermodynamics and the Smarr relation hold. We then take a further step by adding a cosmological constant to the Einstein-Bumblebee theory, and successfully construct a Taub-NUT-AdS-like black hole. We derive all the thermodynamic quantities, including treating the cosmological constant as a pressure, and confirm that the first law and Smarr relation hold as well.

gr-qc↗

arXiv2024

Taub-NUT Black Hole in Higher Derivative Gravity and Its Thermodynamics

We construct the first-order perturbative Taub-NUT black hole solutions in Einstein gravity extended with a cubic curvature invariant. The corrected thermodynamic quantities are then obtained by the standard method and the first law and Smarr relation are satisfied. We also study the perturbative correction to thermodynamics using the Reall-Santos (RS) method and verify that the method is still applicable even though the metrics are no longer asymptotic to Minkowski spacetime. We then apply the RS method to obtain the leading correction to the thermodynamics of the complicated Kerr-Taub-NUT black holes.

gr-qc↗

arXiv2024

New Taub-NUT Black Holes with Massive Spin-2 Hair

We consider Einstein gravity extended with quadratic curvature invariants, where the well-known Ricci-flat Taub-NUT black hole remains a solution. An analysis of the unstable Lichnerowicz modes in the Taub-NUT background enables us to identify the mass and NUT parameters (m,n) where new Taub-NUT black holes can emerge. We then adopt numerical technique to construct these new Taub-NUT black holes that bifurcate away from the Ricci-flat ones. Unlike the Ricci-flat Taub-NUT, there can exist two new black holes for an appropriate given temperature, making it a total of three if we include the Ricci-flat one.

gr-qc↗

arXiv2024

A Regularized $(XP)^2$ Model

We investigate a dynamic model described by the classical Hamiltonian $H(x,p)=(x^2+a^2)(p^2+a^2)$, where $a^2>0$, in classical, semi-classical, and quantum mechanics. In the high-energy $E$ limit, the phase path resembles that of the $(XP)^2$ model. However, the non-zero value of $a$ acts as a regulator, removing the singularities that appear in the region where $x, p \sim 0$, resulting in a discrete spectrum characterized by a logarithmic increase in state density. Classical solutions are described by elliptic functions, with the period being determined by elliptic integrals. In semi-classical approximation, we speculate that the asymptotic Riemann-Siegel formula may be interpreted as summing over contributions from multiply phase paths. We present three different forms of quantized Hamiltonians, and reformulate them into the standard Schr\" odinger equation with $\cosh 2x$-like potentials. Numerical evaluations of the spectra for these forms are carried out and reveal minor differences in energy levels. Among them, one interesting form possesses Hamiltonian in the Schr\" odinger equation that is identical to its classical version. In such scenarios, the eigenvalue equations can be expressed as the vanishing of the Mathieu functions' value at $i\infty$ points, and furthermore, the Mathieu functions can be represented as the wave functions.

quant-ph↗

arXiv2015

Relativistic corrections to $Υ$ exclusive decay into double $S-$wave charmonia

Within the framework of nonrelativisitic QCD factorization formalism, we present the next-to-leading-order relativistic corrections to $Υ$ exclusive decay into $η_c$ plus $J/ψ$. The double charmonia can be produced through several immediate channels, i.e. $Υ\to g^*g^*g^*\to η_c+J/ψ$, $Υ\to g^*g^*γ^*\to η_c+J/ψ$, and $Υ\to γ^*\to η_c+J/ψ$. The amplitudes of these three channels are obtained accurate up to ${\cal O}(α_s^3 v^2)$, ${\cal O}(αα_s^2 v^2)$, and ${\cal O}(αα_s^2 v^2)$ respectively, where $v$ indicates the typical heavy quark velocity in bottomonium and/or charmonium rest frame. The decay rates are also presented. We find the next-to-leading-order relativistic corrections to the short distance coefficients as well as the decay rates are both significant and negative, especially for the corrections from bottomonium. More seriously, the decay rates are even brought into negative by including the relativistic corrections, which indicates the poor convergence for the velocity expansion in this kind of processes. Detailed analysis is given in the paper.

hep-ph↗

arXiv2013

Positronium decay in a circular polarized laser field

We calculate the lifetime of both the o-Ps and the p-Ps positronium annihilation decay $ Ps\toγγ$ in the strong circular polarized laser field. We take a strategy of the factorization to separate the effects caused by the Coulomb interaction and the strong laser field interaction. It is factorized in the time direction but not in the space direction. Our results show that in the laser with long wavelength and high intensity, the lifetimes of those Ps states are dramatically increased. For $\rm CO_2$ laser with $10\, μm$ wavelength and $10^{13} W/cm^2$ intensity, lifetime of the spin-single positronium is increased by $10^8$ times. Our result is consistent with those obtained by solving the Sch{ö}dinger equation. This effect may be useful for the high harmonic generation(HHG) effects provided with the Ps\cite{keitel2004}.

hep-ph↗

arXiv2012

Order-$v^4$ Relativistic Corrections to $Υ$ Inclusive Decay into a Charm pair

In this work, we determine the short-distance coefficients for $Υ$ inclusive decay into a charm pair through relative order $v^4$ within the framework of NRQCD factorization formula. The short-distance coefficient of the order-$v^4$ color-singlet NRQCD matrix element is obtained through matching the decay rate of $b\bar{b}(^3S^{[1]}_1)\to c\bar{c}gg$ in full QCD to that in NRQCD. The double and single IR divergences appearing in the decay rate are exactly canceled through the next-to-next-to-leading-order renormalization of the operator ${\mathcal O}(^3S^{[8]}_1)$ and the next-to-leading-order renormalization of the operators ${\mathcal O}(^3P^{[8]}_J)$. To investigate the convergence of the relativistic expansion arising from the color-singlet contributions, we study the ratios of the order-$v^2$ and -$v^4$ color-singlet short-distance coefficients to the leading-order one. Our results indicate that though the order-$v^4$ color-singlet short-distance coefficient is quite large, the relativistic expansion for the color-singlet contributions in the process $Υ\to c\bar{c}+X$ is well convergent due to a small value of $v$. In addition, we extrapolate the value of the mass ratio of the charm quark to the bottom quark, and find the relativistic corrections rise quickly with increase of the mass ratio.

hep-ph↗

arXiv2012

Relativistic corrections to the semi-inclusive decay of $\bmψ$ and $\bmΥ$

In the framework of the nonrelativistic quantum chromodynamics factorization formalism, we study the processes of $ψ(nS)$ and $Υ(nS)$ decay into a lepton pair or a charm pair associated with two jets up to the next-to-leading order in velocity expansion. We present the analytic expressions for the differential decay rate to the invariant mass of the lepton pair or charm pair. We find that the ratio of the next-to-leading order short-distance coefficient to the leading order one is in the range from -5.5 to -12.4. The relativistic corrections are so large that they modify the leading order prediction significantly. Utilizing the analytic expressions, we also investigate the relativistic corrections in different kinematic regions and their dependence on the masses of the initial-state quarkonium and the final-state fermion. In addition, we study the momentum distribution of $D^{*+}$ in the process $Υ(1S)\to c\bar{c}gg\to D^{*+}X$.

hep-ph↗

arXiv2011

Production of Triply Heavy Baryons at LHC

Triply heavy baryons are very interesting hadrons to be explored for they provide particular information about strong interactions, hadron structures, and weak decays of heavy baryons. We calculate the hadronic production cross sections of the Ω_{ccc} and the Ω_{ccb}, which are dominated by the gg fusion subprocesses containing 4362 and 1454 Feynman diagrams, respectively. A method for generating and calculating tree level Feynman diagrams automatically is developed to deal with complicated processes containing so many diagrams. Our results show that 10^4-10^5 events of triply heavy baryons can be accumulated for 10 fb^{-1} integrated luminosity at LHC. Signatures of the triply heavy baryons are pointed out, with emphasis on the decay modes Ω_{ccc} -> Ω_{sss} + 3 π^+ and Ω_{ccb} -> Ω_{sss} + 3 π^+ +π^-. We conclude that it is quite promising to discover them at LHC.

hep-ph↗

arXiv2011

Production of four-quark states with double heavy quarks at LHC

We study the hadronic production of four-quark states with double heavy quarks and double light antiquarks at LHC. The production mechanism is that a color anti-triplet diquark cluster consisting of double heavy quarks is formed first from the produced double heavy quark-antiquark pairs via $gg$ fusion hard process, followed by the fragmentation of the diquark cluster into a four-quark (tetraquark) state. Predictions for the production cross sections and their differential distributions are presented. Our results show that it is quite promising to discover these tetraquark states in LHC experiments both for large number events and for their unique signatures in detectors.

hep-ph↗

arXiv2010

Higher Order Corrections to the Cross Section of e+e- to Quarkonium plus gamma

The production cross sections of $e^+e^- $ to a heavy quarkonium with $C$-parity even $S-$wave and $P-$wave associated with a photon are analyzed in the framework of non-relativistic Quantum Chromodynamics(NRQCD) factorization formalism. The short-distance coefficients are determined up to the next-to-leading order(NLO) QCD radiative corrections for $S-$ and $P-$wave and NLO relativistic corrections for $S-$wave in analytical forms. Applying the results to estimate the cross sections we find that both the radiative and relativistic corrections are considerable.

hep-ph↗

arXiv2007

QCD corrections to single slepton production at hadron colliders

We evaluate the cross section for single slepton production at hadron colliders in supersymmetric theories with R-parity violating interactions to the next-to-leading order in QCD. We obtain fully differential cross section by using the phase space slicing method. We also perform soft-gluon resummation to all order in $α_s$ of leading logarithm to obtain a complete transverse momentum spectrum of the slepton. We find that the full transverse momentum spectrum is peaked at a few GeV, consistent with the early results for Drell-Yan production of lepton pairs. We also consider the contribution from gluon fusion via quark-triangle loop diagrams dominated by the $b$-quark loop. The cross section of this process is significantly smaller than that of the tree-level process induced by the initial $b\bar{b}$ annihilation.

hep-ph↗

arXiv2004

A Comprehensive Four-Quark Interpretation of D_s(2317), D_s(2457) and D_s(2632)

The recently observed new member of the charm-strange family D_s(2632) which has a surprisingly narrow width is challenging our theory. D_s(2317) and D_s(2457) which were observed earlier have similar behaviors and receive various theoretical explanations. Some authors use the heavy hadron chiral effective theory to evaluate heavy-light quark systems and obtain a reasonable evaluation on the masses of D_s(2317) and D_s(2457). An alternative picture is to interpret them as four-quark or molecular states. In this work, we are following the later and propose a unitive description for all the three new members D_s(2632), D_s(2317) and D_s(2457) and at least, so far our picture is consistent with the data.

hep-ph↗

arXiv2003

Renormalization in Reparameterization Invariance

The renormalization issue of the reparameterization invariance in heavy quark effective theory and NRQCD is investigated. I argue that the renormalization of the transformation of the heavy quark field under the variation of the velocity parameter V is attributed to the renormalization of the small component field in the proposed transformation. I show that the matching condition for determining the renormalized small component field can be obtained by imposing an infinitesimal transformation of V on the relations between the Green's functions in QCD full theory and those in the effective theory. As an application, I determine the renormalized transformation to order 1/m^2 using the matching condition. The obtained result is in disagreement with that determined by indirect method.

hep-ph↗

arXiv2002

The meson $B_c$ annihilation to leptons and inclusive light hadrons

The annihilation of the $B_c$ meson to leptons and inclusive light hadrons is analyzed in the framework of nonrelativistic QCD (NRQCD) factorization. We find that the decay mode, which escapes from the helicity suppression, contributes a sizable fraction width. According to the analysis, the branching ratio due to the contribution from the color-singlet component of the meson $B_c$ can be of order (10^{-2}). We also estimate the contributions from the color-octet components. With the velocity scaling rule of NRQCD, we find that the color-octet contributions are sizable too, especially, in certain phase space of the annihilation they are greater than (or comparative to) the color-singlet component. A few observables relevant to the spectrum of charged lepton are suggested, that may be used as measurements on the color-octet and color-singlet components in the future $B_c$ experiments. A typical long distance contribution in the annihilation is estimated too.

hep-ph↗

arXiv2001

Resummation of QCD Corrections to the eta_c Decay Rate

We examine the ratio of the decay rate of the eta_c into light hadrons to the decay rate into photons and find that most of the large next-to-leading-order (NLO) correction is associated with running of the strong coupling alpha_s. We resum such contributions by analyzing final-state chains of vacuum-polarization bubbles. We show that the nonperturbative parts of the bubble chains can be absorbed into a color-octet matrix element, once one has used contour deformations of the phase-space integrals to cancel certain contributions. We argue that these contributions are incompatible with the uncertainty principle. We also argue that perturbation theory is reliable only if one carries out the phase-space integrations before the perturbation summation. Our results are in good agreement with experiment and differ considerably from those that one obtains by applying the scale-setting method of Brodsky, Lepage, and Mackenzie to the NLO result.

hep-ph↗