Nambu–Jona-Lasinio模型：高温下的逆磁催化效应

37 浏览量更新于2024-09-03 收藏 330KB PDF 举报

"Nambu–Jona-Lasinio模型中超出平均场的逆磁催化" 在物理学领域，Nambu–Jona-Lasinio (NJL) 模型是一种广泛用于描述量子色动力学（QCD）低能量行为的有效理论模型。这个模型由Yoichiro Nambu和Giacomo Jona-Lasinio于1961年提出，它通过四费米子相互作用来模拟强相互作用，尤其是在夸克和介子层次上。NJL模型在理解凝聚态物理、核物理和粒子物理中的某些现象时非常有用，因为它能够解释基本粒子如夸克的束缚行为，以及它们如何形成更复杂的粒子，比如介子。在给定的研究中，学者们关注的是在强磁场环境中NJL模型中的一个特殊现象，即逆磁催化（Inverse Magnetic Catalysis，IMC）。通常情况下，强磁场会促进夸克物质中电荷对称性破缺，这一过程被称为磁催化（Magnetic Catalysis，MC）。然而，对于某些物理系统，在高温条件下，情况恰恰相反，磁场反而会减弱这种电荷对称性的破缺，这就是逆磁催化。在这项研究中，作者超越了平均场近似（Mean Field Approximation），这意味着他们考虑了更复杂的量子涨落和非线性效应，这些效应在简单的平均场处理中通常被忽略。他们发现，尽管在低温下，磁催化仍然是主导效应，但随着温度升高，情况会发生变化。在高磁场和高温的组合下，由于Pauli-Villars正则化方案中Goldstone模的尺寸减小，介子打扮的夸克质量会下降。Goldstone模是与自发对称性破缺相关的波动模式，这里的“介子打扮的夸克”指的是介子与夸克之间的相互作用导致的夸克性质改变。 Pauli-Villars正则化是一种技术，用于消除量子场论中的一些无穷大，以得到有意义的结果。在本研究中，这个正则化方法揭示了磁场对Goldstone模的影响，进而影响到夸克的质量行为。这一发现对于理解QCD在极端条件下的行为，比如宇宙早期状态或高密度天体（如中子星）的内部环境，具有重要意义。这项研究深化了我们对NJL模型在强磁场和高温环境下的理解，特别是揭示了逆磁催化的机制。这不仅有助于理论物理学家精确预测QCD相图，也为实验物理学家提供了新的探索方向，例如在高能物理实验（如RHIC或LHC）中寻找这些效应的证据。同时，这也可能对核物质性质的计算，以及在天体物理和宇宙学中的应用产生影响。

Physics Letters B 758 (2016) 195–199

Contents lists available at ScienceDirect

Physics Letters B

www.elsevier.com/locate/physletb

Inverse magnetic catalysis in Nambu–Jona-Lasinio model beyond mean

ﬁeld

Shijun Mao

School of Science, Xian Jiaotong University, Xian 710049, China

a r t i c l e i n f o a b s t r a c t

Article history:

Received

23 February 2016

Received

in revised form 14 April 2016

Accepted

6 May 2016

Available

online 10 May 2016

Editor:

J.-P. Blaizot

Keywords:

Inverse

magnetic catalysis

Nambu–Jona-Lasinio

model

Beyond

mean ﬁeld

We study inverse magnetic catalysis in the Nambu–Jona-Lasinio model beyond mean ﬁeld approximation.

The feed-down from mesons to quarks is embedded in an effective coupling constant at ﬁnite

temperature and magnetic ﬁeld. While the magnetic catalysis is still the dominant effect at low

temperature, the meson dressed quark mass drops down with increasing magnetic ﬁeld at high

temperature due to the dimension reduction of the Goldstone mode in the Pauli–Villars regularization

scheme.

(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP

The Quantum Chromodynamics (QCD) phase transition in an

external magnetic ﬁeld has drawn much attention in recent years,

due to its close relation to high energy nuclear collisions [1–9],

compact stars [10–21] and cosmological phase transitions [22–25].

Considering the dimension reduction of fermions, the chiral sym-

metry

breaking is enhanced by the magnetic ﬁeld, which leads to

an increasing critical temperature for the chiral restoration phase

[26–28]. However, the lattice simulation of QCD performed with

physical pion mass observes the opposite phenomenon, namely

the critical temperature drops down with increasing magnetic ﬁeld

[29–32]. Many scenarios are proposed to understand this inverse

magnetic catalysis [33–48], such as the magnetic inhibition of

mesons, the mass gap in the large N

limit, the sphalerons, the

gluon screening effect, and the weakening of the strong coupling.

the NJL model without external magnetic ﬁeld, the mean

ﬁeld approximation for quarks together with the random phase

approximation for mesons can describe well the chiral thermody-

namics

of hot and dense quark–meson plasma [49–53], and the

feed-down from mesons to quarks leads to a lower critical tem-

perature [54].

With a strong magnetic ﬁeld, the Goldstone mode

in the chiral symmetry breaking phase may play an important role

for the realization of inverse magnetic catalysis [33]. One problem

in the NJL model is the regularization. Since the model with con-

tact

interaction among quarks is nonrenormalizable, one requires

a regularization scheme to avoid the divergent momentum inte-

E-mail address: maosj08@mails.tsinghua.edu.cn.

grations. When the external magnetic ﬁeld is turned on, the quark

energy becomes discrete and the phase space becomes anisotropy.

In this case taking a proper regularization scheme becomes signiﬁ-

cant

to guarantee the law of causality, see the following discussion.

this Letter, we focus on the inverse magnetic catalysis re-

sulted

from the Goldstone mode at strong magnetic ﬁeld. In the

framework of the NJL model, we will calculate the effective quark

coupling constant by including the feed-down from the Goldstone

mode and solve the corresponding gap equation for the chiral con-

densate.

We will see that the regularization scheme here plays an

important role.

The

SU(2) NJL model is deﬁned through the Lagrangian density

[49–53]

L =



iγ

−m



ψ +





ψψ





iγ



τ ψ





(1)

where the covariant derivative D

= ∂

+ iQ A

couples quarks

to the external magnetic ﬁeld B = (0, 0, B) =∇×A along the

z-axis, Q =diag (Q

, Q

) =dia g (

e, −

e) is the quark charge ma-

trix

in ﬂavor space, and G is the coupling constant in the scalar

and pseudo-scalar channels. In chiral limit with vanishing current

quark mass m

= 0, the SU(2)

⊗ SU(2)

symmetry is broken

down to U(1)

⊗ U (1)

by the magnetic ﬁeld B, and the number

of Goldstone modes is reduced from 3 to 1. In the chiral symme-

try

breaking phase, quarks obtain mass m =m

−G

ψψ from the

chiral condensate 

ψψ.

With the Leung–Ritus–Wang method [55–62], the quark propa-

gator

with ﬂavor f in coordinate space can be written as

http://dx.doi.org/10.1016/j.physletb.2016.05.018

0370-2693/

SCOAP

下载后可阅读完整内容，剩余4页未读，立即下载

weixin_38522106

粉丝: 2
资源: 901

Nambu–Jona-Lasinio模型：高温下的逆磁催化效应

夸克热和磁化夸克物质的中子介子性质：一种新的与磁场无关的正则化方案，应用于NJL型模型

Nambu–Jona-Lasinio模型中强磁夸克物质状态方程的各向异性

磁化夸克物质的介子性质

Nambu–Jona-Lasinio模型中磁场对夸克物质剪切粘度的影响

球体中的Nambu–Jona-Lasinio模型

Nambu–Jona-Lasinio模型中对相图的正则化依赖性

饱和Nambu–Jona-Lasinio模型中的对称能和中子星特性

有限尺度Nambu–Jona-Lasinio模型的通货膨胀

具有两种矢量相互作用的强磁场下三味Nambu–Jona-Lasinio模型中的夸克磁场

SU（3）Nambu–Jona-Lasinio模型中带电场的Schwinger机理

最新资源