arXiv subjects

Yong-Hui Qi

Publications and source records attributed to Yong-Hui Qi.

14 recordsLinked to original sources

arXiv2023

Superradiance in the Kerr-Taub-NUT spacetime

Superradiance is the effect of field waves being amplified during reflection from a charged or rotating black hole. In this paper, we study the low-energy dynamics of super-radiant scattering of massive scalar and massless higher spin field perturbations in a generic axisymmetric stationary Kerr-Taub-NUT (Newman-Unti-Tamburino) spacetime, which represents sources with both gravitomagnetic monopole moment (magnetic mass) and gravitomagnetic dipole moment (angular momentum). We obtain a generalized Teukolsky master equation for all spin perturbation fields. The equations are separated into their angular and radial parts. The angular equations lead to spin-weighted spheroidal harmonic functions that generalize those in Kerr spacetime. We identify an effective spin as a coupling between frequency (or energy) and the NUT parameter. The behaviors of the radial wave function near the horizon and at the infinite boundary are studied. We provide analytical expressions for low-energy observables such as emission rates and cross sections of all massless fields with spin, including scalar, neutrino, electromagnetic, Rarita-Schwinger, and gravitational waves.

gr-qc↗

arXiv2022

Effective field theories for gapless phases with fractons via a coset construction

Fractons are particles with restricted mobility. We give a symmetry-based derivation of effective field theories of gapless phases with fractonic topological defects, such as solids and supersolids, using a coset construction. The resulting theory is identified as the Cosserat elasticity theory, which reproduces the conventional symmetric elasticity theory at low energies. The construction can be viewed as a dynamical realization of the inverse Higgs mechanism. We incorporate topological defects such as dislocations and disclinations, which are nontrivially related by the Bianchi identities of defect gauge fields. The origin of the fractonic nature of defects in those systems can be traced back to the semidirect product structure of translational and rotational groups. The construction is immediately extendable to higher dimensions and systems with broken translational symmetries, such as solids, supersolids, and vortex crystals. We identify Wess-Zumino terms in supersolids, which induce quasiparticle scatterings on topological defects.

cond-mat.str-el↗

arXiv2019

Effective Field Theory Perspective on Next-to-Minimal Composite Higgs

We study both the CP-even and CP-odd effective chiral Lagrangians of next minimal composite Higgs model {with symmetry breaking pattern depicted by the coset $SO(6)/SO(5)$} through the sigma/omega decomposition, in which the Goldstone matrix of the coset is decomposed in terms of the standard model Higgs doublet and an additional scalar singlet $s$ at the electroweak scale. The effective Lagrangian is described by the electroweak chiral Lagrangian up to $p^4$ order, with a function dependence on the Higgs boson and new scalar $s$, named Higgs function. This function in the effective Lagrangian incorporates the Higgs non-linearity or vacuum misalignment effects in the next minimal composite Higgs model, due to the Riemann curvature on the Nambu-Goldstone bosons scalar manifold, leads to various Higgs couplings deviated from the standard model ones, and also indicates the relations among different Higgs couplings in the low energy. Matching to the Higgs effective field theory below the electroweak scale, we obtain various low energy observables such as the electroweak oblique parameters, anomalous triple and quartic gauge couplings, anomalous couplings of Higgs to gauge bosons, in which the Higgs non-linearity effects are encoded in the ratio $ξ\equiv v^2/f^2$ of the electroweak scale and the new physics scale.

hep-ph↗

arXiv2019

Quantum Correction to Chaos in Schwarzian Theory

We discuss the quantum correction to chaos in the Schwarzian theory. We carry out the semi-classical analysis of the Schwarzian theory to study Feynman diagrams of the Schwarzian soft mode. We evaluate the contribution of the soft mode to the out-of-time-order correlator up to order $\mathcal{O}(g^4)$. We show that the quantum correction of order $\mathcal{O}(g^4)$ by the soft mode decreases the maximum Lyapunov exponent $2π/ β$.

hep-th↗

arXiv2018

Mott transition with Holographic Spectral function

We show that the Mott transition can be realized in a holographic model of a fermion with bulk mass, $m$, and a dipole interaction of coupling strength $p$. The phase diagram contains gapless, pseudo-gap and gapped phases and the first one can be further divided into four sub-classes. We compare the spectral densities of our holographic model with the Dynamical Mean Field Theory (DMFT) results for Hubbard model as well as the experimental data of Vanadium Oxide materials. Interestingly, single-site and cluster DMFT results of Hubbard model share some similarities with the holographic model of different parameters, although the spectral functions are quite different due to the asymmetry in the holography part. The theory can fit the X-ray absorption spectrum (XAS) data quite well, but once the theory parameters are fixed with the former it can fit the photoelectric emission spectrum (PES) data only if we symmetrize the spectral function.

hep-th↗

arXiv2018

Schwarzian correction to quantum correlation in SYK model

We study a class of SYK-type models in large N limit from the gravity dual side in terms of Schwarzian action analytically. The quantum correction to two point correlation function due to the Schwarzian action produces transfer of degree of freedom from the quasiparticle peak to Hubbard band in density of states (DOS), a signature strong correlation. In Schwinger-Keldysh (SK) formalism, we calculate higher point thermal out-of-time order correlation (OTOC) functions, which indicate quantum chaos by having Lyapunov exponent. Higher order local spin-spin correlations are also calculated, which can be related to the dynamical local susceptibility of quantum liquids such as spin glasses, disordered metals.

hep-th↗

arXiv2016

Topological Non-Fermi Liquid

In this paper we investigate the $(2+1)$-dimensional topological non-Fermi liquid in strongly correlated electron system, which has a holographic dual description by Einstein gravity in $(3+1)$-dimensional anti-de Sitter (AdS) space-time. In a dyonic Reissner-Nordstrom black hole background, we consider a Dirac fermion coupled to the background $U(1)$ gauge theory and an intrinsic chiral gauge field $b_M$ induced by chiral anomaly. UV retarded Green's function of the charged fermion in the UV boundary from AdS$_4$ gravity is calculated, by imposing in-falling wave condition at the horizon. We also obtain IR correlation function of the charged fermion at the IR boundary arising from the near horizon geometry of the topological black hole with index $k=0,\pm 1$. By using the UV retarded Green's function and IR correlation function, we analyze the low frequency behavior of the topological non-Fermi liquid at zero and finite temperatures, especially the relevant non-Fermi liquid behavior near the quantum critical region. In addition, we find that when $k=\pm 1$, the effective mass of bulk Dirac fermion at IR fixed point is topologically quantized, consequently the Fermi momentum presents a discrete sparse distributed pattern, in contrary to the Ricci flat case with $k=0$. As demonstrated examples, we calculate the spectral functions of topological non-Fermi liquid due to anomalous Hall effect (AHE) ($|\vec{b}|\ne 0, b_0=0$) and chiral magnetic effect (CME) ($|\vec{b}| = 0, b_0\ne 0$), which can be tested in topological materials such as topological insulator and topological metal with strong couplings.

hep-th↗

arXiv2015

Topolgical Charged Black Holes in Generalized Horava-Lifshitz Gravity

As a candidate of quantum gravity in ultrahigh energy, the $(3+1)$-dimensional Hořava-Lifshitz (HL) gravity with critical exponent $z\ne 1$, indicates anisotropy between time and space at short distance. In the paper, we investigate the most general $z=d$ Hořava-Lifshitz gravity in arbitrary spatial dimension $d$, with a generic dynamical Ricci flow parameter $λ$ and a detailed balance violation parameter $ε$. In arbitrary dimensional generalized HL$_{d+1}$ gravity with $z\ge d$ at long distance, we study the topological neutral black hole solutions with general $λ$ in $z=d$ HL$_{d+1}$, as well as the topological charged black holes with $λ=1$ in $z=d$ HL$_{d+1}$. The HL gravity in the Lagrangian formulation is adopted, while in the Hamiltonian formulation, it reduces to Dirac$-$De Witt's canonical gravity with $λ=1$. In particular, the topological charged black holes in $z=5$ HL$_6$, $z=4$ HL$_5$, $z=3,4$ HL$_4$ and $z=2$ HL$_3$ with $λ=1$ are solved. Their asymptotical behaviors near the infinite boundary and near the horizon are explored respectively. We also study the behavior of the topological black holes in the $(d+1)$-dimensional HL gravity with $U(1)$ gauge field in the zero temperature limit and finite temperature limit, respectively. Thermodynamics of the topological charged black holes with $λ=1$, including temperature, entropy, heat capacity, and free energy are evaluated.

hep-th↗

arXiv2012

Incompressible Navier-Stokes Equations from Einstein Gravity with Chern-Simons Term

In (2+1)-dimensional hydrodynamic systems with broken parity, the shear and bulk viscosity is joined by the Hall viscosity and curl viscosity. The dual holographic model has been constructed by coupling a pseudo scalar to the gravitational Chern-Simons term in (3+1)-dimensional bulk gravity. In this paper, we investigate the non-relativistic fluid with Hall viscosity and curl viscosity living on a finite radial cutoff surface in the bulk. Employing the non-relativistic hydrodynamic expansion method, we obtain the incompressible Navier-Stokes equations with Hall viscosity and curl viscosity. Unlike the shear viscosity, the ratio of the Hall viscosity over entropy density is found to be cutoff scale dependent, and it tends to zero when the cutoff surface approaches to the horizon of the background spacetime.

hep-th↗

arXiv2010

Anomalous gauge couplings of the Higgs boson at the LHC II: Study of additional backgrounds in semileptonic mode of WW scatterings

Searching for the Higgs boson is of first priority in LHC experiments. Once a Higgs candidate is found, we then need to know whether it is the standard model (SM) Higgs boson or a Higgs boson in new physics beyond the SM. So far we do not know what model of new physics will actually reflect the property of the nature. A model-independent way of measuring the anomalous couplings of the Higgs boson will provide a no-lose study, i.e., if we find nonvanishing anomalous couplings (deviation from the SM couplings), we can conclude that it is a new physics effect. In a previous paper \cite{QKLZ09}, we gave a hadron level study of a model-independent test of the anomalous gauge couplings of the Higgs boson at the 14 TeV LHC via the semileptonic mode of weak-boson scatterings $pp\to W^+W^\pm j^f_1 j^f_2\to l^+ν^{}_lj^{}_1j^{}_2j^f_1j^f_2$, and the conclusion is that, with certain kinematical cuts imposed, the measurement can start for an integrated luminosity of 50 fb$^{-1}$. For higher integrated luminosity, say 100 fb$^{-1}$, the two main anomalous coupling constants $f^{}_{WW}/Λ^2$ and $f^{}_W/Λ^2$ can be determined separately which may provide a clue for figuring out the underlying theory of new physics.

hep-ph↗

arXiv2010

Topological Interactions in the Higgsless Model at the LHC

Topological quantum interactions, namely Chern-Simons terms and global Wess-Zumino terms, arise naturally in theories with extra dimensions of space compactified on orbifolds. If the extra dimensions become manifest at the TeV scale, experiments at the Large Hadron Collider (LHC) could observe signatures of topological interactions. Decays of Kaluza-Klein excitations of neutral electroweak gauge bosons into pairs of neutral Standard Model gauge bosons, ZZ and Z+photon, would provide a clean signature, since such decays do not occur at tree level. In this paper, we investigate the prospects for discovering such decays at the LHC, in the context of the Higgsless model of electroweak symmetry breaking. We identify the form of the relevant topological interactions, and estimate their strength. We find that in the minimal version of the model, the signal may be observed with about 100 inverse fb of data at the LHC using the Drell-Yan production process of the Kaluza-Klein gauge bosons. In addition, it is likely that the ultraviolet completion of the model would contain additional massive fermions, which can significantly enhance the signal. With two additional fermion multiplets, observation of the topological decay modes at the 3-sigma level would be possible with about 100 inverse fb of data using the highly model-independent vector boson fusion production channel.

hep-ph↗

arXiv2009

Discovery Potential of New Boson $W_1^{\pm}$ in the Minimal Higgsless Model at LHC

In this paper, we demonstrate the LHC discovery potential of new charged vector boson $W_1^{\pm}$ predicted by the Minimal Higgsless model in the process $pp\to W_1^{\pm}qq^{\prime}\to W^{\pm}Z^0qq^\prime\to \ell^{\pm}\ell^+\ell^-νqq^{\prime}(\ell=e,μ)$ by analyzing the generator level events of the signal and backgrounds. The generator for the signal $pp \to {W_1}^{\pm}qq^\prime\to W^{\pm}Z^0qq^\prime$ at tree level is developed with the Minimal Higgsless model and then interfaced with PYTHIA for the parton showers and hadronization. The backgrounds are produced with PYTHIA and ACERMC. We give integrated luminosities required to discover 5$σ$ signal as a function of $W_1^{\pm}$ mass.

hep-ex↗

arXiv2009

Anomalous gauge couplings of the Higgs boson at the CERN LHC: Semileptonic mode in WW scatterings

We make a full tree level study of the signatures of anomalous gauge couplings of the Higgs boson at the CERN LHC via the semileptonic decay mode in WW scatterings. Both signals and backgrounds are studied at the hadron level for the Higgs mass in the range 115 GeV to 200 GeV. We carefully impose suitable kinematical cuts for suppressing the backgrounds. To the same sensitivity as in the pure leptonic mode, our result shows that the semileptonic mode can reduce the required integrated luminosity by a factor of 3. If the anomalous couplings in nature are actually larger than the sensitivity bounds shown in the text, the experiment can start the test for an integrated luminosity of 50 inverse fb.

hep-ph↗

arXiv2008

LHC Signatures of New Gauge Bosons in the Minimal Higgsless Model

We study the LHC signatures of new gauge bosons in the gauge-invariant minimal Higgsless model. It predicts an extra pair of W_1 and Z_1 bosons which can be as light as ~400GeV and play a key role in the delay of unitarity violation. We analyze the W_1 signals in pp --> W_0Z_0Z_0 --> jj4\ell and pp --> jj W_0Z_0 --> jj3\ellνprocesses at the LHC, including the complete electroweak and QCD backgrounds. We reveal the complementarity between these two channels for discovering the W_1 boson, and demonstrate the LHC discovery potential over the full range of allowed W_1 mass.

hep-ph↗