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Yu-Zhu Chen

Publications and source records attributed to Yu-Zhu Chen.

14 recordsLinked to original sources
arXiv2025

Quantum Statistics Forbids Particle Exchange Statistics beyond Bosons and Fermions in 3D

Quantum matter in three spatial dimensions is observed to consist exclusively of bosons and fermions. Whether this empirical fact follows from basic consistency requirements of quantum theory itself or must be imposed as an additional principle has for 80 years remained a fundamental conceptual gap. Here we close this gap by establishing a no-go theorem that excludes any particle exchange statistics beyond bosons and fermions in three dimensions. We identify the consistency conditions linking the many-body Hilbert-space structure of quantum mechanics with the statistical microstate counting of indistinguishable particles. As a corollary, we demonstrate that higher-dimensional representations of the symmetric group cannot give rise to genuinely distinct particle exchange statistics in any spatial dimension.

quant-ph↗
arXiv2022

Constructing effective action for gravitational field by effective potential method

The aim of this paper is to construct a quantum effective action for gravitational fields by the effective potential method in quantum field theory. The minimum of the quantum effective action gives an equation of quantum fluctuations. We discuss the quantum fluctuation in the flat spacetime and in the Schwarzschild spacetime. It is shown that a baby spacetime may be created from a classical vacuum through a quantum fluctuation.

gr-qc↗
arXiv2022

Scattering state and bound state of scalar field in Schwarzschild spacetime: Exact solution

The main aim of this paper is twofold. (1) Exact solutions of a scalar field in the Schwarzschild spacetime are presented. The exact wave functions of scattering states and bound-states are presented. Besides the exact solution, we also provide explicit approximate expressions for bound-state eigenvalues and scattering phase shifts. (2) By virtue of the exact solutions, we give a direct calculation for the discontinuous jump on the horizon for massive scalar fields, while in literature such a jump is obtained from an asymptotic solution by an analytic extension treatment.

gr-qc↗
arXiv2021

Multipole moment and singular source in Newtonian gravity and in Einstein gravity

The multipole moments are defined as the multipole expansion coefficients of the gravitational field at infinity. In Newtonian gravity, the multipole moments are determined by the source distribution -- the multipole integrals of the source. In this paper, we show that the multipole moments in general relativity cannot be determined by the multipole integrals of the source. We provide the multipole integrals in static axial spacetimes, such as, the Curzon spacetime. The Curzon spacetime possesses the same multipole integrals of the source with the Schwarzschild spacetime, while they possess different multipole moments.

gr-qc↗
arXiv2021

Quantum correction of gravitational constant

We suggest a scheme for considering the quantum correction of the gravitational constant. In the model, the gravitational constant originates from a coupling of the gravitational field with a scalar field. In this paper, we show that if the scalar field, as it should be in the real physical world, is a quantum field, then the gravitational constant will have a spacetime-dependent quantum correction, so that the quantum corrected physical constant is no longer a constant. The quantum correction of the gravitational constant is different in different spacetime. We calculate the quantum correction in the Schwarzschild spacetime, the $H_{3}$ (Euclidean $AdS_{3}$) spacetime, the $H_{3}/Z$ spacetime, the universe model, the de Sitter spacetime, and the Rindler spacetime.

gr-qc↗
arXiv2021

Gravitational wave scattering theory without large-distance asymptotics

In conventional gravitational wave scattering theory, a large-distance asymptotic approximation is employed. In this approximation, the gravitational wave is approximated by its large-distance asymptotics. In this paper, we establish a gravitational wave scattering theory without the large-distance asymptotic approximation.

gr-qc↗
arXiv2021

Converting Lattices into Networks: The Heisenberg Model and Its Generalizations with Long-Range Interactions

In this paper, we convert the lattice configurations into networks with different modes of links and consider models on networks with arbitrary numbers of interacting particle-pairs. We solve the Heisenberg model by revealing the relation between the Casimir operator of the unitary group and the conjugacy-class operator of the permutation group. We generalize the Heisenberg model by this relation and give a series of exactly solvable models. Moreover, by numerically calculating the eigenvalue of Heisenberg models and random walks on network with different numbers of links, we show that a system on lattice configurations with interactions between more particle-pairs have higher degeneracy of eigenstates. The highest degeneracy of eigenstates of a lattice model is discussed.

math-ph↗
arXiv2020

Toy models of black hole, white hole and wormhole: thermal effects and information loss problem

In this paper, by setting proper boundaries in the Minkowski spacetime, we construct three toy model spacetimes, a toy black hole, a toy white hole, and a toy wormhole. Based on these model spacetimes, we discuss the Hawking radiation and the information loss problem. By counting the number of the field modes inside and outside the horizon, we show the thermal radiation of the toy black hole. We show that the white hole have a thermal absorption. We show that in the whole toy wormhole spacetime, there is no information lost. In addition, we show the black hole radiation and the white hole absorption are independent of the choices of boundary conditions at the singularity. We also show the physical effects caused by two particular boundary conditions.

gr-qc↗
arXiv2020

Cylindrical gravitational waves: radiation and resonance

In the weak field approximation the gravitational wave is approximated as a linear wave, which ignores the nonlinear effect. In this paper, we present an exact general solution of the cylindrical gravitational wave. The exact solution of the cylindrical gravitational wave is far different from the weak field approximation. This solution implies the following conclusions. (1) There exist gravitational monopole radiations in the cylindrical gravitational radiation. (2) The gravitational radiation may generate the resonance in the spacetime. (3) The nonlinearity of the gravity source vanishes after time averaging, so the observed result of a long-time measurement may be linear.

physics.gen-ph↗
arXiv2017

A 1+5-dimensional gravitational-wave solution: curvature singularity and spacetime singularity

We solve a $1+5$-dimensional cylindrical gravitational-wave solution of the Einstein equation, in which there are two curvature singularities. Then we show that one of the curvature singularities can be removed by an extension of the spacetime. The result exemplifies that the curvature singularity is not always a spacetime singularity; in other words, the curvature singularity cannot serve as a criterion for spacetime singularities.

gr-qc↗
arXiv2017

Why the entropy of spacetime is independent of species of particles -- the species problem

The Hawking radiation emits all species of particles, but the Bekenstein-Hawking entropy is independent of the number of the species of particles. This is the so-called species problem --- a puzzling problem for a long time. In this paper, we suggest a solution to this problem. A result of the scheme is that the black hole atmosphere has a mass equaling 3/8 mass of a classical Schwarzschild black hole, which agrees with 't Hooft's brick wall model.

gr-qc↗
arXiv2016

Optical Properties of Synthetic Cannabinoids with Negative Indexes

Some kinds of psychoactive drugs have the structures which are called split-ring resonators (SRRs). SRRs might result in negative permittivity and permeability simultaneously in electromagnetic field. Simultaneous negative indexes can lead to the famous phenomenon of negative refraction. This optical property makes it possible to distinguish synthetic cannabinoids from other abusive psychoactive drugs in the UV-vis region. This optical method is non-damaged and superior in forensic science. In this paper, we use tight-binding model calculating the permittivity and permeability of the main ingredients of synthetic cannabinoids. At the same time, we give two more results of zolpidem and caffeine. Further we discuss the negative refraction of the category of zepam qualitatively.

physics.chem-ph↗
arXiv2015

Thermo field dynamics approach for entropy of spacetime

A thermo field dynamics approach for calculating the entropy of a spacetime is suggested. It is exemplified through the Rindler spacetime, the Milne spacetime, the Boulware spacetime, and the Minkowski spacetime with a moving mirror that the entropy of a spacetime is equal to the entropy of a thermo quantum field with the same temperature of the spacetime we study. This in fact suggests an thermo field dynamics approach of calculating the entropy of a spacetime. In this approach, the entropy of a spacetime is an expectation value of the entropy operator on a thermo vacuum state. The thermo vacuum state is the vacuum state on the maximal manifold which is the maximal analytic extension of the spacetime we study.

gr-qc↗