Instantons and Chiral Symmetry

AbstractAlthough a prototypical Su–Schrieffer–Heeger (SSH) soliton exhibits various important topological concepts including particle-antiparticle (PA) symmetry and fractional fermion charges, there have been only few advances in exploring such properties of topological solitons beyond the SSH model. Here, by considering a chirally extended double-Peierls-chain model, we demonstrate novel PA duality and fractional charge e/2 of topological chiral solitons even under the chiral symmetry breaking. This provides a counterexample to the belief that chiral symmetry is necessary for such PA relation and fractionalization of topological solitons in a time-reversal invariant topological system. Furthermore, we discover that topological chiral solitons are re-fractionalized into two subsolitons which also satisfy the PA duality. As a result, such dualities and fractionalizations support the topological $$\mathbb {Z}_4$$ Z 4 algebraic structures. Our findings will inspire researches seeking feasible and promising topological systems, which may lead to new practical applications such as solitronics.

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Fate of false vacua in holographic first-order phase transitions

Journal of High Energy Physics ◽

10.1007/jhep12(2020)200 ◽

2020 ◽

Vol 2020 (12) ◽

Author(s):

Francesco Bigazzi ◽

Alessio Caddeo ◽

Aldo L. Cotrone ◽

Angel Paredes

Keyword(s):

Phase Transitions ◽

Chiral Symmetry ◽

Metastable Phase ◽

Chiral Symmetry Breaking ◽

Model Parameters ◽

Temperature Phase ◽

Thin Wall ◽

Critical Temperatures ◽

First Order ◽

First Order Phase

Abstract Using the holographic correspondence as a tool, we study the dynamics of first-order phase transitions in strongly coupled gauge theories at finite temperature. Considering an evolution from the large to the small temperature phase, we compute the nucleation rate of bubbles of true vacuum in the metastable phase. For this purpose, we find the relevant configurations (bounces) interpolating between the vacua and we compute the related effective actions. We start by revisiting the compact Randall-Sundrum model at high temperature. Using holographic renormalization, we compute the derivative term in the effective bounce action, that was missing in the literature. Then, we address the full problem within the top-down Witten-Sakai-Sugimoto model. It displays both a confinement/deconfinement and a chiral symmetry breaking/restoration phase transition which, depending on the model parameters, can happen at different critical temperatures. For the confinement/deconfinement case we perform the numerical analysis of an effective description of the transition and also provide analytic expressions using thick and thin wall approximations. For the chiral symmetry transition, we implement a variational approach that allows us to address the challenging non-linear problem stemming from the Dirac-Born-Infeld action.

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Chiral symmetry and taste symmetry from the eigenvalue spectrum of staggered Dirac operators

Physical Review D ◽

10.1103/physrevd.104.014508 ◽

2021 ◽

Vol 104 (1) ◽

Author(s):

Hwancheol Jeong ◽

Chulwoo Jung ◽

Seungyeob Jwa ◽

Jangho Kim ◽

Jeehun Kim ◽

...

Keyword(s):

Chiral Symmetry ◽

Dirac Operators ◽

Eigenvalue Spectrum

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