Possible Instability of the Ground State of Two-Flavour Colour Superconductor Induced by Colour Neutrality

The diquark condensate susceptibility in neutral colour superconductor at moderate baryon density is calculated in the frame of the two-flavour Nambu-Jona-Lasinio model with the mean field approximation. When colour chemical potential is introduced to keep charge neutrality, the dlquark condensate susceptibility ＆ negative in the directions without diquark condensate in colour space, which may be regarded as a signal of the instability of the conventional ground state with only diquark condensate in the colour-3 direction.

Continuous-Mixture Autoregressive Networks Learning the Kosterlitz–Thouless Transition

We develop deep autoregressive networks with multi channels to compute many-body systems with continuous spin degrees of freedom directly.As a concrete example,we demonstrate the two-dimensional XY model with the continuous-mixture networks and rediscover the Kosterlitz–Thouless(KT)phase transition on a periodic square lattice.Vortices characterizing the quasi-long range order are accurately detected by the generative model.By learning the microscopic probability distributions from the macroscopic thermal distribution,the networks are trained as an efficient physical sampler which can approximate the free energy and estimate thermodynamic observables unbiasedly with importance sampling.As a more precise evaluation,we compute the helicity modulus to determine the KT transition temperature.Although the training process becomes more time-consuming with larger lattice sizes,the training time remains unchanged around the KT transition temperature.The continuousmixture autoregressive networks we developed thus can be potentially used to study other many-body systems with continuous degrees of freedom.

Building imaginary-time thermal field theory with artificial neural networks

In this paper,we introduce a novel approach in quantum field theories to estimate actions using artificial neural networks(ANNs).The actions are estimated by learning system configurations governed by the Boltzmann factor,e^(-s),at different temperatures within the imaginary time formalism of thermal field theory.Specifically,we focus on the 0+1 dimensional quantum field with kink/anti-kink configurations to demonstrate the feasibility of the method.Continuous-mixture autoregressive networks(CANs)enable the construction of accurate effective actions with tractable probability density estimation.Our numerical results demonstrate that this methodology not only facilitates the construction of effective actions at specified temperatures but also adeptly estimates the action at intermediate temperatures using data from both lower and higher temperature ensembles.This capability is especially valuable for detailed exploration of phase diagrams.

Investigation of the tetraquark states QqQq in the improved chromomagnetic interaction model

In the framework of the improved chromomagnetic interaction model,we complete a systematic study of the S-wave tetraquark states QqQq(Q=c,b,and q=u,d,s)with different quantum numbers:J^(PC)=0^(+(+)),1^(+(±)),and 2^(+(+)).The mass spectra of tetraquark states are predicted,and the possible decay channels are analyzed by considering both the angular momentum and C-parity conservation.The recently observed hidden-charm tetraquark states with strangeness,such as Z_(cs)(3985)^(-),X(3960),and Z_(cs)(4220)^(+),can be well explained in our model.Additionally,according to the wave function of each tetraquark state,we find that the low-lying states of each QqQq configuration have a large overlap to the QQ and qq meson basis,instead of the Qq and qQ meson basis.This indicates that one can search these tetraquark states in future experiments via the channel of QQ and qq mesons.

Quarksonic matter at high isospin density

Analogous to the quarkyonic matter at high baryon density in which the quark Fermi seas and the baryonic excitations coexist, it is argued that a ＂quarksonic matter＂ phase appears at high isospin density where the quark （antiquark） Fermi seas and the mesonic excitations coexist. We explore this phase in detail in both large Nc and asymptotically free limits. In the large Nc limit, we sketch a phase diagram for the quarksonic matter. In the asymptotically free limit, we study the pion superfluidity and thermodynamics of the quarksonic matter by using both perturbative calculations and an effective model.

Ginzburg–Landau Free Energy of Crystalline Color Superconductors:A Matrix Formalism from Solid-State Physics

The Ginzburg–Landau(GL) free energy of crystalline color superconductors is important for understanding the nature of the phase transition to the normal quark matter and predicting the preferred crystal structure. So far the GL free energy at zero temperature has only been evaluated up to the sixth order in the condensate. To give quantitative reliable predictions we need to evaluate the higher-order terms. In this work,we present a new derivation of the GL free energy by using the discrete Bloch representation of the fermion field. This derivation introduces a simple matrix formalism without any momentum constraint,which may enable us to calculate the GL free energy to arbitrary order by using a computer.