Topological Origin of Chiral Symmetry Breaking in QCD and in Gravity
نویسنده
چکیده
We show that the assumption of non-zero topological susceptibility of the vacuum in a fermion-free version of a theory, such as gravity or QCD, suffices to conclude the following: Once Nf massless fermion flavors are added to the theory, they break the chiral flavor symmetry dynamically, down to a subgroup that would be anomaly-free under gauging; In both theories, the pseudo-Goldstone corresponding to axial U(1)-symmetry becomes massive; In QCD as well as in gravity the massless fermions are eliminated from the low energy spectrum of the theory. All the above conclusions are reached without making an assumption about confinement. Some key methods of our approach are: Reformulation of topological susceptibility in the language of a 3-form gauge theory; Utilization of gravity in the role of a spectator interaction for the chiral anomaly-matching in QCD; Gauging chiral symmetries and matching their anomalies using the spectator Green-Schwarz type axions. Our observations suggest that breaking of chiral symmetries in QCD and in gravity can be described in unified topological language, and seemingly-disconnected phenomena, such as, the generation of η′-mass in QCD and breaking of global chiral symmetry by gravity may share a secret analogy. The described phenomenon may shed a new light via contribution of micro black holes into the gravitational topological susceptibility of the vacuum on incompatibility between black holes and global symmetries. It appears that explicit breaking is not the sole possibility, and like QCD, gravity may break global symmetries dynamically. As an useful byproduct, matching of gravitational anomalies provides a selection tool for compositeness, eliminating possibility of massless composite fermions where standard gauge anomaly matching would allow for their existence.
منابع مشابه
Proposal for Topologically Unquenched QCD
A proposal is presented for simulating an improvement on quenched QCD with dynamical fermions which interact with the gluon configuration only via the topological index of the latter. Strengths and shortcomings of the method are discussed and it is argued that the approximation – though being crude – shares some qualitative aspects of full QCD which relate to the issue of chiral symmetry breaking.
متن کاملThe fate of UA(1) and topological features of QCD at finite temperature
The nature of chiral phase transition for QCD with two light quark flavors is not yet completely resolved. This is primarily because one has to understand whether or not the anomalous U(1) symmetry in the flavor sector is effectively restored along with the chiral symmetry. Since the physics near the chiral phase transition is essentially non-perturbative, we employ first principles lattice tec...
متن کاملChiral symmetry breaking driven by dilaton
A supersymmetric gauge theory with flavor quark is studied in a dual supergravity by adding a D7-brane probe into the AdS background deformed by the dilaton. This background exhibits quark-confinement and gluon condensation in the dual gauge theory. By estimating the vev of flavor quark-bilinear in the gravity dual, we find spontaneous chiral symmetry breaking and simultaneous supersymmetry bre...
متن کاملTopological Charge and U(1)a Symmetry in the High Temperature Phase of Qcd
We discuss the global symmetries of the high temperature phase of QCD with Nf massless quarks. We show that the U(Nf ) × U(Nf ) symmetries are only violated by operators of dimension ≥ 3Nf . For Nf > 2 this implies that the thermal two-point correlation functions of the η′ and πa’s are identical. We discuss the implications of this for the chiral phase transition at finite temperature. nick@zen...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2017