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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.
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| Item type | Article | ||||
| Journal or Publication Title | Physical Review D | ||||
| Publisher | AMER PHYSICAL SOC | ||||
| Open Access Type | SCOAP3 | ||||
| Place of Publication | COLLEGE PK | ||||
| Volume | 99 | ||||
| Number of Issue or Book Chapter | 7 | ||||
| Page Range | 074515-1-074515-21 | ||||
| Date | 30 April 2019 | ||||
| Date of publication | 06 Apr 2021 13:51 | ||||
| Institutions | Physics > Institute of Theroretical Physics > Chair Professor Braun > Group Tilo Wettig | ||||
| Identification Number |
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| Keywords | OPERATOR; INSTANTONS; PHASE; | ||||
| Dewey Decimal Classification | 500 Science > 530 Physics | ||||
| Status | Published | ||||
| Refereed | Yes, this version has been refereed | ||||
| Created at the University of Regensburg | Yes | ||||
| URN of the UB Regensburg | urn:nbn:de:bvb:355-epub-455076 | ||||
| Item ID | 45507 |
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