arXiv subjects

Yi-Xin Chen

Publications and source records attributed to Yi-Xin Chen.

At least 19 recordsLinked to original sources

arXiv2025

QCD sum rule analysis of $0^{+}$ four-quark states

We present a comprehensive QCD sum rules analysis at next-to-leading order for all types of $J^P=0^{+}$ four-quark states composed of $u$, $d$, and $s$ quarks. The eigenvectors of the renormalization matrix are chosen to be the renormalized four-quark operators, which can be equally interpreted as tetraquark or molecule operators. Meanwhile, the typical nonet masses given by bare tetraquark operators are lower than those given by bare molecule operators. Most of the nonet masses are around $1-2\text{GeV}$, and they can be interpreted as the $0^+$ mesons observed in experiments. We find a category of four-quark nonets with masses $\lesssim1\text{GeV}$, potentially corresponding to the light $0^+$ mesons $f_0(500)$, $K^*_0(700)$, $f_0(980)$, and $a_0(980)$. On the other hand, the possible 27-fold states are heavier than most of the nonets, with masses $\gtrsim 2\text{GeV}$. The main uncertainty arises from the factorization of high-dimensional condensates, which usually underestimates their values. To address this, we introduce deviation factors for the dimension-6, -8, and -10 condensates, and vary them over a wide range to obtain conservative estimates of the $0^+$ four-quark state masses. Some general properties of the $0^+$ light four-quark states can be derived that do not rely on precise numerical values. We also find that the ambiguity in the factorization of the dimension-8 condensate can introduce a larger discrepancy than previously estimated. As a byproduct, we propose a simple trick for renormalizing multi-quark operators at the one-loop level.

hep-ph↗

arXiv2021

A cosmic accelerated scenario based on degrees of freedom of the spacetime

Several recent investigations have shown that there is a holographic relationship between the bulk degrees of freedom and the surface degrees of freedom in the spacetime. Furthermore, the entropy on the horizon can produce an entropic force effect on the bulk degrees of freedom. In this paper, we explore the dynamic evolution law of the universe based on the idea of the entropic force and asymptotically holographic equipartition and further analyze the thermodynamic properties of the current model. We get the age of the universe, the relation between the luminosity distance and the redshift factor and the deceleration parameter which are consistent with astronomical observations. In addition, we can well explain the age of the universe and the mechanism of accelerated expansion without introducing dark energy for the evolution history of the universe up to now. We also show that the generalized second law of thermodynamics, the energy balance condition and the energy equipartition relation always hold. More importantly, the energy balance condition is indeed a holographic relation between the bulk degrees of freedom and the surface degrees of freedom of the spacetime. Finally, we analyze the energy conditions and show that the strong energy condition is always violated and the weak energy condition is satisfied when $t\leq2t_{0}$ in which $t$ is the time parameter and $t_{0}$ is the age of the universe.

gr-qc↗

arXiv2019

Cosmological scenario based on the particle creation and holographic equipartition

We propose a cosmological scenario which describes the evolution history of the universe based on the particle creation and holographic equipartition. The model attempts to solve the inflation of the early universe and the accelerated expansion of the present universe without introducing the dark energy from the perspective of thermodynamics. Throughout the evolution of the universe, we assume that the universe always creates particles in some way and holographic equipartition is always satisfied. Further, we choose that the creation rate of particles is proportional to $H^{2}$ in the early universe and to $H$ in the present and late universe, where $H$ is the Hubble parameter. Then we obtain the solutions $a(t)\propto e^{αt/3}$ and $a(t)\propto t^{1/2}$ for the early universe and the solutions $a(t)\propto t^δ$ and $a(t)\propto e^{Ht}$ for the present and late universe, where $α$ and $δ$ are the parameters. Finally, we obtain and analyze two important thermodynamic properties for the present model.

gr-qc↗

arXiv2019

Correlated coherence as resource of remote state preparation and quantum teleportation

Quantum discord and quantum entanglement are resources in some quantum information processing (QIP) models. However, in recent years, the evidence that separable states or classically correlated states can also accomplish QIP is demonstrated. It provides a useful tool since such states are easier to prepare. Quantum coherence is a measure of non-classical correlation, containing entanglement and discord as a subset. Nowadays, it is of interest whether quantum coherence can act as a resource in QIP independently or not, without the help from quantum discord or entanglement. In this paper, we show that quantum correlated coherence(a measure of coherence with local parts removed) is also a kind of quantum resource. It is the sufficient and necessary resource for quantum remote state preparation and quantum teleportation.

quant-ph↗

arXiv2018

Thermodynamics in the universe described by the emergence of the space and the energy balance relation

It has previously been shown that it is more general to describe the evolution of the universe based on the emergence of the space and the energy balance relation. Here we investigate the thermodynamic properties of the universe described by such a model. We show that the first law of thermodynamics and the generalized second law of thermodynamics (GSLT) are both satisfied and the weak energy condition are also fulfilled for two typical examples. Finally we examine the physical consistency for the present model.

gr-qc↗

arXiv2017

Accelerated Expansion of the Universe based on Emergence of Space and Thermodynamics of the Horizon

Researches in the several decades have shown that the dynamics of gravity is closely related to thermodynamics of the horizon. In this paper, we derive the Friedmann acceleration equation based on the idea of "emergence of space" and thermodynamics of the Hubble horizon whose temperature is obtained from the unified first law of thermodynamics. Then we derive another evolution equation of the universe based on the energy balance relation $ρV_{H}=TS$. Combining the two evolution equations and the equation of state of the cosmic matter, we obtain the evolution solutions of the FRW universe. We find that the solutions obtained by us include the solutions obtained in the standard general relativity(GR) theory. Therefore, it is more general to describe the evolution of the universe in the thermodynamic way.

gr-qc↗

arXiv2016

Deterministic remote preparation of an arbitrary qubit state using a partially entangled state and finite classical communication

We propose a deterministic remote state preparation (RSP) scheme for preparing an arbitrary (including pure and mixed) qubit, where a partially entangled state and finite classical communication are used. To our knowledge, our scheme is the first RSP scheme that fits into this category. One other RSP scheme proposed by Berry shares close features, but can only be used to prepare an arbitrary pure qubit. Even so, our scheme saves classical communication by approximate 1 bit per prepared qubit under equal conditions. When using a maximally entangled state, the classical communication for our scheme is 2 bits, which agrees with Lo's conjecture on the resource cost. Furthermore Alice can switch between our RSP scheme and a standard teleportation scheme without letting Bob know, which makes the quantum channel multipurpose.

quant-ph↗

arXiv2016

Emergence of space and cosmic evolution based on entropic force

In this paper, we propose a model in which an additional pressure due to the effects of the entropic force is added to the ideal fluid. Furthermore, we obtain the dynamic equation in the FRW universe which contains the quantum gravitational effects based on the description of entropic force and emergence of space. Our model can well explain the age of the universe and the effect of the current accelerating expansion. We give the relation between the luminosity distance and the redshift factor, and compare this relation with that of lambda cold dark matter model($ΛCDM$ model).

hep-th↗

arXiv2016

A general thermodynamical description of the event horizon in the FRW universe

The Friedmann equation in the Friedmann-Robertson-Walker(FRW) universe with any spatial curvature is derived from the first law of thermodynamics on the event horizon. The key idea is to redefine a Hawking temperature on the event horizon. Furthermore, we obtain the evolution equations of the universe including the quantum correction and explore the evolution of the universe in the $f(R)$ gravity. In addition, we also investigate the generalized second law of thermodynamics in Einstein gravity and the $f(R)$ gravity. This perspective also implies that the first law of thermodynamics on the event horizon have a general description in respect of the evolution of the FRW universe.

hep-th↗

arXiv2015

Nonthermal Spectrum of Hawking Radiation

We show that for the thermal spectrum of Hawking radiation black hole's information loss paradox may still be present, even if including the entanglement information stored in the entangled Minkowski vacuum. And to avoid this inconsistency, the spectrum of Hawking radiation must be nonthermal. After reconsidering the derivation of Hawking effect, we find that the thermal spectrum is actually resulted from the geometric optics approximation in deriving the Bogolubov coefficients. When treated a little more accurately, we obtain some nonthermal spectrum for the Hawing radiation, which reduces to the thermal one in the geometric optics approximation.

hep-th↗

arXiv2015

Hawking Effect as Quantum Inertial Effect

We show that "particle production" by gravitational field, especially the Hawking effect, may be treated as some quantum inertial effect, with the energy of Hawking radiation as some vacuum energy shift. This quantum inertial effect is mainly resulted from some intrinsical energy fluctuation $\hbarκ/c$ for a black hole. In particular, there is an extreme case in which $\hbarκ/c$ is the Planck energy, giving a "Planck black hole" whose event horizon's diameter is one Planck length. Moreover, we also provide a possibility to obtain some positive cosmological constant for an expanding universe, which is induced from the vacuum energy shift caused by quantum inertial effect.

hep-th↗

arXiv2015

Black Hole Thermodynamics Based on Unitary Evolutions

In this paper, we try to construct black hole thermodynamics based on the fact that, the formation and evaporation of a black hole can be described by quantum unitary evolutions. First, we show that the Bekenstein-Hawking entropy $S_{BH}$ may not be a Boltzmann or thermal entropy. To confirm this statement, we show that the original black hole's "first law" may not simply be treated as the first law of thermodynamics formally, due to some missing metric perturbations caused by matter. Then, by including those (quantum) metric perturbations, we show that the black hole formation and evaporation can be described in a unitary manner effectively, through a quantum channel between the exterior and interior of the event horizon. In this way, the paradoxes of information loss and firewall can be resolved effectively. Finally, we show that black hole thermodynamics can be constructed in an ordinary way, by constructing statistical mechanics.

hep-th↗

arXiv2015

"Almost" Quotient Space, Non-dynamical Decoherence and Quantum Measurement

An alternative approach to decoherence, named non-dynamical decoherence is developed and used to resolve the quantum measurement problem. According to decoherence, the observed system is open to a macroscopic apparatus(together with a possible added environment) in a quantum measurement process. We show that this open system can be well described by an "almost" quotient Hilbert space formed phenomenally according to some stability conditions. A group of random phase unitary operators is introduced further to obtain an exact quotient space for the observed system. In this quotient space, a density matrix can be constructed to give the Born's probability rule, realizing a (non-dynamical) decoherence. The concept of the ("almost") quotient space can also be used to explain the classical properties of a macroscopic system. We show further that the definite outcomes in a quantum measurement are mainly caused by the "almost" quotient space of the macroscopic apparatus.

quant-ph↗

arXiv2015

Statistical Mechanics Derived From Quantum Mechanics

A pedagogical derivation of statistical mechanics from quantum mechanics is provided, by means of open quantum systems. Besides, a new definition of Boltzmann entropy for a quantum closed system is also given to count microstates in a way consistent with the superposition principle. In particular, this new Boltzmann entropy is a constant that depends only on the dimension of the system's relevant Hilbert subspace. Finally, thermodynamics for quantum systems is investigated formally.

hep-th↗

arXiv2014

A Unitary Model of The Black Hole Evaporation

A unitary effective field model of the black hole evaporation is proposed to satisfy almost the four postulates of the black hole complementarity (BHC). In this model, we enlarge a black hole-scalar field system by adding an extra radiation detector that couples with the scalar field. After performing a partial trace over the scalar field space, we obtain an effective entanglement between the black hole and the detector (or radiation in it). As the whole system evolves, the S-matrix formula can be constructed formally step by step. Without local quantum measurements, the paradoxes of the information loss and AMPS's firewall can be resolved. However, the information can be lost due to quantum decoherence, as long as some local measurement has been performed on the detector to acquire the information of the radiation in it. But unlike Hawking's completely thermal spectrum, some residual correlations can be found in the radiations. All these considerations can be simplified in a qubit model that provides a \emph{modified quantum teleportation} to transfer the information via an EPR pairs.

hep-th↗

arXiv2014

Optimizing classical communication in remote preparation of a general pure qubit

How to uses shared entanglement and forward classical communication to remotely prepare an arbitrary (mixed or pure) state has been fascinating quantum information scientists. A constructive scheme has been given by Berry for remotely preparing a general pure state with a pure entangled state and finite classical communication. Based on this scheme, for high-dimensional systems it is possible to use a coding of the target state to optimize the classical communication cost. Unfortunately, for low-dimensional systems such as a pure qubit the coding method is inapplicable. Because qubit plays a central role in quantum information theory, we propose an optimization procedure which can be used to minimize the classical communication cost in the remote preparation of a general pure qubit. Interestingly, our optimization procedure is linked to the uniform arrangement of $N$ points on the Bloch sphere, which provides a geometric description.

quant-ph↗

arXiv2013

Thermodynamics of the universe bounded by the cosmological event horizon and dominated by the tachyon fluid

Our aim is to investigate the thermodynamic properties of the universe bounded by the cosmological event horizon and dominated by the tachyon fluid. We give two different laws of evolution of our universe. Further, we show the first law and the generalized second law of thermodynamics (GSLT) are both satisfied in two cases, but their properties of the thermodynamic equilibrium are totally different. Besides, under our solutions, we find the validity of the laws of thermodynamics is irrelevant with the parameters of the tachyon fluid. Finally, we conclude that the universe bounded by the cosmological event horizon and dominated by the tachyon fluid has a good thermodynamic description. In turn, the thermodynamic description can provide a good physical interpretation for the dynamic evolution of our universe due to the equivalence between the first law of thermodynamics and the Friedmann equation to some extent.

gr-qc↗

arXiv2013

Emergence of spaces and the dynamic equations of FRW universes in the $f(R)$ theory and deformed Hořava-Lifshitz theory

It has been shown that Friedmann equation of FRW universe can be derived from the idea which says cosmic space is emergent as cosmic time progresses and our universe is expanding towards the state with the holographic equipartition by Padmanabhan. In this note, we give a general relationship between the horizon entropy and the number of the degrees of freedom on the surface, we also obtain the corresponding dynamic equations by using the idea of emergence of space in the $f(R)$ theory and deformed Hořava-Lifshitz (HL) theory.

hep-th↗