Automatic Fine-Tuning in the Two-Flavor Schwinger Model

I discuss the two-flavor Schwinger model both without and with fermion masses. I argue that the phenomenon of "conformal coalescence," in unparticle physics in which linear combinations of short-distance operators can disappear from the long-distance theory, makes it easy to understand som...

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Bibliographic Details
Published in:Physical review letters 2020-10, Vol.125 (18), p.181601-181601, Article 181601
Main Author: Georgi, Howard
Format: Article
Language:English
Subjects:
Coalescing
Energy theory
Fermions
Flavors
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Summary:I discuss the two-flavor Schwinger model both without and with fermion masses. I argue that the phenomenon of "conformal coalescence," in unparticle physics in which linear combinations of short-distance operators can disappear from the long-distance theory, makes it easy to understand some puzzling features of the model with small fermion masses. In particular, I argue that for an average fermion mass mf and a mass difference δm, so long as both are small compared to the dynamical gauge boson mass m=e2/π, isospin-breaking effects in the low-energy theory are exponentially suppressed by powers of exp[−(m/mf)2/3] even if δm≈mf. In the low-energy theory, this looks like exponential fine-tuning, but it is done automatically by conformal coalescence.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.125.181601