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Kieburg, M. ; Verbaarschot, J. J. M. ; Wettig, T.

Dirac spectrum and chiral condensate for QCD at fixed θ angle

Article

Kieburg, M., Verbaarschot, J. J. M. and Wettig, T. (2019) Dirac spectrum and chiral condensate for QCD at fixed θ angle. Physical Review D 99 (7), 074515-1-074515-21.

DOI to cite this document: 10.5283/epub.45507


Abstract

We analyze the mass dependence of the chiral condensate for QCD at nonzero theta angle and find that in general the discontinuity of the chiral condensate is not on the support of the Dirac spectrum. To understand this behavior we decompose the spectral density and the chiral condensate into contributions from the zero modes, the quenched part, and a remainder which is sensitive to the fermion ...

We analyze the mass dependence of the chiral condensate for QCD at nonzero theta angle and find that in general the discontinuity of the chiral condensate is not on the support of the Dirac spectrum. To understand this behavior we decompose the spectral density and the chiral condensate into contributions from the zero modes, the quenched part, and a remainder which is sensitive to the fermion determinant and is referred to as the dynamical part. We obtain general formulas for the contributions of the zero modes. Expressions for the quenched part, valid for an arbitrary number of flavors, and for the dynamical part, valid for one and two flavors, are derived in the microscopic domain of QCD. We find that at nonzero theta angle the quenched and dynamical parts of the Dirac spectral density are strongly oscillating with an amplitude that increases exponentially with the volume V and a period of order of 1/V. The quenched part of the chiral condensate becomes exponentially large at theta not equal 0, but this divergence is canceled by the contribution from the zero modes. The oscillatory behavior of the dynamical part of the density is essential for moving the discontinuity of the chiral condensate away from the support of the Dirac spectrum. As important by-products of this work we obtain analytical expressions for the microscopic spectral density of the Dirac operator at nonzero theta angle for both one- and two-flavor QCD with nonzero quark masses.



Involved Institutions


Details

Item typeArticle
Journal or Publication TitlePhysical Review D
PublisherAMER PHYSICAL SOC
Open Access TypeSCOAP3
Place of PublicationCOLLEGE PK
Volume99
Number of Issue or Book Chapter7
Page Range074515-1-074515-21
Date30 April 2019
Date of publication06 Apr 2021 13:51
InstitutionsPhysics > Institute of Theroretical Physics > Chair Professor Braun > Group Tilo Wettig
Identification Number
ValueType
10.1103/PhysRevD.99.074515DOI
KeywordsOPERATOR; INSTANTONS; PHASE;
Dewey Decimal Classification500 Science > 530 Physics
StatusPublished
RefereedYes, this version has been refereed
Created at the University of RegensburgYes
URN of the UB Regensburgurn:nbn:de:bvb:355-epub-455076
Item ID45507

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