arXiv subjects

Ji-Chong Yang

Publications and source records attributed to Ji-Chong Yang.

52 records · Page 3Linked to original sources

arXiv2023

QCD on Rotating Lattice with Staggered Fermions

We investigate the finite-temperature quantum chromodynamics (QCD) on a rotating lattice with $N_f=2+1$ staggered fermions and the projective plane boundary condition. We observe a negative rotational rigidity (defined in the main text) and a negative quark spin susceptibility associated with the chiral vortical effect. In contrast to most of the effective model predictions, we find that the chiral condensate decreases and the Polyakov loop increases with imaginary rotation, implying a rotational catalysis of chiral symmetry breaking and confinement by real rotation. We determine the phase boundaries for both chiral and confinement-deconfinement phase transitions on the $Ω_I$-$T$ plane, where $Ω_I$ is the imaginary angular velocity.

hep-lat↗

arXiv2023

Charged-current non-standard neutrino interactions at the LHC and HL-LHC

A series of new physics scenarios predict the existence of the extra charged gauge boson $W'$, which can induce charged-current (CC) non-standard neutrino interactions (NSIs). The theoretical constraints on the simplified $W'$ model and further on the CC NSI parameters $\widetildeε^{ qq'Y}_{αβ}$ from partial wave unitarity and $W'$ decays are considered. The sensitivity of the process $p p \rightarrow W'\rightarrow \ellν$ to the $W'$ model at the LHC and high-luminosity~(HL) LHC experiments is investigated by estimating the expected constraints on $\widetildeε^{qq'Y}_{αβ}$ ($α= β= e $ or $μ$) using a Monte-Carlo~(MC) simulation. We find that the interference effect plays an important role, and the LHC can strongly constrain $\widetildeε^{qq'L}_{αβ}$. Compared with those at the $13 \;{\rm TeV}$ LHC with $\mathcal{L}=139\;{\rm fb}^{-1}$, the expected constraints at the $14 \;{\rm TeV}$ LHC with $\mathcal{L}=3\;{\rm ab}^{-1}$ can be strengthened to approximately one order of magnitude.

hep-ph↗

arXiv2022

Study of the Roberge-Weiss phase caused by external uniform classical electric field using lattice QCD approach

The effect of an external electric field on the quark matter is an important question due to the presence of strong electric fields in heavy ion collisions. In the lattice QCD approach, the case of a real electric field suffers from the `sign problem', and a classical electric field is often used similar as the case of chemical potential. Interestingly, in axial gauge a uniform classical electric field actually can correspond to an inhomogeneous imaginary chemical potential that varies with coordinate. On the other hand, with imaginary chemical potential, Roberge-Weiss~(R-W) phase transition occurs. In this work, the case of a uniform classical electric field is studied by using lattice QCD approach, with the emphasis on the properties of the R-W phase. Novel phenomena show up at high temperatures. It is found that, the chiral condensation oscillates with $z$ at high temperatures, and so is the absolute value of the Polyakov loop. It is verified that the charge density also oscillates with $z$ at high temperatures. The Polyakov loop can be described by an ansatz $A_p+\sum _{q=u,d} C_q\exp\left(L_τ Q_q iazeE_z\right)$, where $A_p$ is a complex number and $C_d>0,C_u\geq 0$ are real numbers that are fitted for different temperatures and electric field strengths. As a consequence, the behavior of the phase of Polyakov loop is different depending on whether the Polyakov loop encloses the origin, which implies a possible phase transition.

hep-lat↗

arXiv2022

Higgs mode in $2+1$ dimensional $O(2)$ model

We investigate the spectral functions of the Higgs mode in $O(2)$ model, which can be experimentally realized in a 2D Bose gas. Zero temperature limit is considered. Our calculation fully includes the 2-loop contributions. Peaks show up in the spectral functions of both the longitudinal and the scalar susceptibilities. Thus this model cannot explain the disappearance of the response at the weak interaction limit. Neither it can explain the similarity between the longitudinal and the scalar susceptibilities in the visibility of the Higgs mode. A possible lower peak at about $2m_σ$ is also noted.

hep-ph↗

arXiv2022

Effective field theory of the Higgs mode in a two-dimensional dilute Bose gas

We investigate the spectral function of the Higgs mode in a two dimensional Bose gas, by using the effective field theory in the zero temperature limit. Our approach explains the experimental feature that the peak of the spectral function is a soft continuum rather than a sharp peak, broadened and vanishing in the superfluid phase, which cannot be explained in terms of the $O(2)$ model. We also find that the scalar susceptibility is the same as the longitudinal susceptibility.

cond-mat.quant-gas↗

arXiv2021

Optimize quantum simulation using a force-gradient integrator

Quantum simulation has shown great potential in many fields due to its powerful computational capabilities. However, the limited fidelity can lead to a severe limitation on the number of gate operations, which requires us to find optimized algorithms. Trotter decomposition and high order Trotter decompositions are widely used in quantum simulations. We find that they can be significantly improved by force-gradient integrator in lattice QCD. By using two applications as examples, we show that the force-gradient decomposition can reduce the number of gate operations up to about a third of those using high order Trotter decompositions. Therefore, force-gradient decomposition shows a great prospective in future applications of quantum simulation.

quant-ph↗

arXiv2021

The relation between the radii and the densities of magnetic skyrmions

Compared with the traditional magnetic bubble, skyrmion has smaller size, better stability therefore is considered as a very promising candidate for future memory devices. When skyrmions are manipulated, erased and created, the density of skyrmions can be varied, however the relationship between the radii and the densities of skyrmions needs more exploration. In this paper, we study this problem both theoretically and by using the lattice simulation. The average radius of skyrmions as a function of material parameters, the strength of external magnetic field and the density of skyrmions is obtained and verified. With this explicit function, the skyrmion radius can be easily predicted, which is helpful for the future study of skyrmion memory devices.

cond-mat.str-el↗

arXiv2020

Standard Model of Particle Physics Violating Crypto-Nonlocal Realism

It has been well established that quantum mechanics (QM) violates Bell inequalities (BI), which are consequences of local realism (LR). Remarkably QM also violates Leggett inequalities (LI), which are consequences of a class of nonlocal realism called crypto-nonlocal realism (CNR). Both LR and CNR assume that measurement outcomes are determined by preexisting objective properties, as well as hidden variables (HV) not considered in QM. We extend CNR and LI to include the case that the measurement settings are not externally fixed, but determined by hidden variables (HV). We derive a new version of LI, which is then shown to be violated by entangled $B_d$ mesons, if charge-conjugation-parity (CP) symmetry is indirectly violated, as indeed established. The experimental result is quantitatively estimated by using the indirect CP violation parameter, and the maximum of a suitably defined relative violation is about $2.7\%$. Our work implies that standard model (SM) of particle physics violates CNR. Our LI can also be tested in other systems such as photon polarizations.

hep-ph↗

arXiv2020

Circuit-based digital adiabatic quantum simulation and pseudoquantum simulation as new approaches to lattice gauge theory

Gauge theory is the framework of the Standard Model of particle physics and is also important in condensed matter physics. As its major non-perturbative approach, lattice gauge theory is traditionally implemented using Monte Carlo simulation, consequently it usually suffers such problems as the Fermion sign problem and the lack of real-time dynamics. Hopefully they can be avoided by using quantum simulation, which simulates quantum systems by using controllable true quantum processes. The field of quantum simulation is under rapid development. Here we present a circuit-based digital scheme of quantum simulation of quantum $\mathbb{Z}_2$ lattice gauge theory in $2+1$ and $3+1$ dimensions, using quantum adiabatic algorithms implemented in terms of universal quantum gates. Our algorithm generalizes the Trotter and symmetric decompositions to the case that the Hamiltonian varies at each step in the decomposition. Furthermore, we carry through a complete demonstration of this scheme in classical GPU simulator, and obtain key features of quantum $\mathbb{Z}_2$ lattice gauge theory, including quantum phase transitions, topological properties, gauge invariance and duality. Hereby dubbed pseudoquantum simulation, classical demonstration of quantum simulation in state-of-art fast computers not only facilitates the development of schemes and algorithms of real quantum simulation, but also represents a new approach of practical computation.

quant-ph↗

arXiv2019

Entangled baryons: violation of Inequalities based on local realism assuming dependence of decays on hidden variables

Bell inequalities are consequences of local realism while violated by quantum mechanics. In particle physics, entangled high energy particles can be produced from a common source, and the decay of each particle plays the role of measurement. However, in a hidden variable theory, the decay could be determined by hidden variables. This loophole killed such approaches to Bell test in particle physics. It is a special form of measurement-setting or free-will loophole, which also exists in other systems. Using entangled baryons, we present new inequalities of local realism with the explicit assumption of the dependence of the decays on hidden variables, as well as the consideration of the statistical mixture of polarizations and the separation of local hidden variables for objects with spacelike distances. These violations closes the measurement-setting loophole once and for all. We propose to use the processes $η_c\to Λ\barΛ$ and $χ_{c0} \to Λ\barΛ$ to test our inequalities, and show that their violations are likely to be observed with the data already collected in BESIII.

hep-ph↗

arXiv2019

Shape of a skyrmion

We propose a method of determining the shape of a two-dimensional magnetic skyrmion, which can be parameterized as the position dependence of the orientation of the local magnetic moment, by using the expansion in terms of the eigenfunctions of the Schrödinger equation of a harmonic oscillator. A variational calculation is done, up to the next-to-next-to-leading order. This result is verified by a lattice simulation based on Landau-Lifshitz-Gilbert equation. Our method is also applied to the dissipative matrix in the Thiele equation as well as two interacting skyrmions in a bilayer system.

cond-mat.str-el↗

arXiv2019

Generation of magnetic skyrmions through pinning effect

Based on analytical estimation and lattice simulation, a proposal is made that magnetic skyrmions can be generated through the pinning effect in 2D chiral magnetic materials, in absence of an external magnetic field or magnetic anisotropy. In our simulation, stable magnetic skyrmions can be generated in the pinning areas. The properties of the skyrmions are studied for various values of ferromagnetic exchange strength and the Dzyaloshinskii-Moriya interaction strength.

cond-mat.str-el↗

arXiv2016

Factorization of Radiative Leptonic Decays of $B^-$ and $D^-$ Mesons Including the Soft Photon Region

In this work, we study the radiative leptonic decays of $B^-$ and $D^-$ mesons using factorization approach. Factorization is proved to be valid explicitly at 1-loop level at any order of $O(Λ_{\rm QCD}\left/m_Q\right.)$. We consider the contribution in the soft photon region that $E_γ \sim \left. Λ^2_{\rm QCD} /\right. m_Q$. The numerical results shows that, the soft photon region is very important for both the $B$ and $D$ mesons. The branching ratios of $B\to γeν_e$ is $5.21\times 10^{-6}$, which is about $3$ times of the result obtained by only considering the hard photon region $E_γ\sim m_Q$. And for the case of $D\to γeν_e$, the result of the branching ratio is $1.92\times 10^{-5}$.

hep-ph↗

arXiv2015

Effect of the Charged Higgs Bosons in the Radiative Leptonic Decays of $B^-$ and $D^-$ Mesons

In this work, we study the radiative leptonic decays of $B^-$ and $D^-$ mesons in the standard model and the two-Higgs-doublet-model type II. The results are obtained using the factorization procedure, and the contribution of the order $O(Λ_{\rm QCD}\left/m_Q\right.)$ is included. The numerical results are calculated using the wave-function obtained in relativistic potential model. As a result, the decay mode $B\to γτν_τ$ is found to be sensitive to the effect of the charged Higgs boson. Using the constraint on the free parameters of the two Higgs doublet model given in previous works, we find the contribution of the charged Higgs boson in the decay mode $B\to γτν_τ$ can be as large as about $13\%$.

hep-ph↗

arXiv2014

Factorization of Radiative Leptonic Decays of $B^-$ and $D^-$ Mesons

In this work, we study the factorization of the radiative leptonic decays of $B^-$ and $D^-$ mesons, the contributions of the order $O(Λ_{\rm QCD}\left/m_Q\right.)$ are taken into account. The factorization is proved to be valid explicitly at the order $O(α_sΛ_{\rm QCD}\left/m_Q\right.)$. The hard kernel is obtained. The numerical results are calculated using the wave-function obtained in relativistic potential model. The $O(Λ_{\rm QCD}\left/m_Q\right.)$ contribution is found to be very important, the correction to the decay amplitudes of $B^-\to γe\barν$ is about $20\% - 30\%$. For $D$ mesons, the $O(Λ_{\rm QCD}\left/m_Q\right.)$ contributions are more important.

hep-ph↗

arXiv2012

Radiative Leptonic Decays of the charged $B$ and $D$ Mesons Including Long-Distance Contribution

In this work we study the radiative leptonic decays of $B^-$, $D^-$ and $D_s^-\to γl \barν$, including both the short-distance and long-distance contributions. The short-distance contribution is calculated by using the relativistic quark model, where the bound state wave function we used is that obtained in the relativistic potential model. The long-distance contribution is estimated by using vector meson dominance model.

hep-ph↗