30 research outputs found
Asymptotic Symmetries and Subleading Soft Photon Theorem in Effective Field Theories
In [1,2] it was shown that the subleading soft photon theorem in tree level
amplitudes in massless QED is equivalent to a new class of symmetries of the
theory parameterized by a vector field on the celestial sphere. In this paper,
we extend these results to the subleading soft photon theorem in any Effective
Field Theory containing photons and an arbitrary spectrum of massless
particles. We show that the charges associated to the above class of symmetries
are sensitive to certain three point functions of the theory and are corrected
by irrelevant operators of specific dimensions. Our analysis shows that the
subleading soft photon theorem in any tree level scattering amplitude is a
statement about asymptotic symmetries of the -matrix.Comment: 26 pages, 3 figure
Asymptotic Symmetries and Weinberg's Soft Photon Theorem in Mink
We show that Weinberg's leading soft photon theorem in massless abelian gauge
theories implies the existence of an infinite-dimensional large gauge symmetry
which acts non-trivially on the null boundaries of
-dimensional Minkowski spacetime. These symmetries are parameterized by
an arbitrary function of the -dimensional celestial sphere
living at . This extends the previously established
equivalence between Weinberg's leading soft theorem and asymptotic symmetries
from four and higher even dimensions to \emph{all} higher dimensions.Comment: 30 pages; v2: Added reference and minor clarification comments, fixed
minor typos, version to appear in JHE
New Symmetries of Massless QED
An infinite number of physically nontrivial symmetries are found for abelian
gauge theories with massless charged particles. They are generated by large
gauge transformations that asymptotically approach an arbitrary function
on the conformal sphere at future null infinity
() but are independent of the retarded time. The value of
at past null infinity () is determined from that on
by the condition that it take the same value at either end of
any light ray crossing Minkowski space. The constant
symmetries are spontaneously broken in the usual vacuum. The associated
Goldstone modes are zero-momentum photons and comprise a boson living on
the conformal sphere. The Ward identity associated with this asymptotic
symmetry is shown to be the abelian soft photon theorem.Comment: 17 pages, v2: typos in equations correcte
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Covariant phase space and soft factorization in non-Abelian gauge theories
Abstract: We perform a careful study of the infrared sector of massless non-abelian gauge theories in four-dimensional Minkowski spacetime using the covariant phase space formalism, taking into account the boundary contributions arising from the gauge sector of the theory. Upon quantization, we show that the boundary contributions lead to an infinite degeneracy of the vacua. The Hilbert space of the vacuum sector is not only shown to be remarkably simple, but also universal. We derive a Ward identity that relates the n-point amplitude between two generic in- and out-vacuum states to the one computed in standard QFT. In addition, we demonstrate that the familiar single soft gluon theorem and multiple consecutive soft gluon theorem are consequences of the Ward identity
Phase Space Renormalization and Finite BMS Charges in Six Dimensions
We perform a complete and systematic analysis of the solution space of
six-dimensional Einstein gravity. We show that a particular subclass of
solutions -- those that are analytic near -- admit a
non-trivial action of the generalised Bondi-Metzner-van der Burg-Sachs (GBMS)
group which contains \emph{infinite-dimensional} supertranslations and
superrotations. The latter consists of all smooth volume-preserving
DiffWeyl transformations of the celestial . Using the covariant
phase space formalism and a new technique which we develop in this paper (phase
space renormalization), we are able to renormalize the symplectic potential
using counterterms which are \emph{local} and \emph{covariant}. We then
construct charges which faithfully represent the GBMS algebra and in doing so,
settle a long-standing open question regarding the existence of GBMS symmetries
in higher dimensional non-linear gravity. Finally, we show that the
semi-classical Ward identities for the supertranslations and superrotations are
precisely the leading and subleading soft-graviton theorems respectively.Comment: 75 pages, 1 figur
New phases of SYM at finite chemical potential
We do a systematic search of supergravity solutions that, via the
AdS/CFT correspondence, are dual to thermal states in
SYM at finite chemical potential. These solutions dominate the microcanonical
ensemble and are required to ultimately reproduce the microscopic entropy of
AdS black holes. Using a mix of analytical and numerical methods, we construct
and study static charged hairy solitonic and black hole solutions with global
AdS asymptotics. They are constructed in two distinct consistent
truncations of five dimensional gauged supergravity (and can thus be uplifted
to asymptotically AdSS solutions of type IIB supergravity). In
the "single charge" truncation which consists of one charged scalar field,
hairy black holes exist above a critical charge and merge with the known
Cvetic-L\"u-Pope (CLP) black holes along a curve determined by the onset of
superradiance in the latter family. The lowest mass hairy black hole is a
singular zero entropy soliton. In the "two charge" truncation which consists of
a two equal charged scalar fields, hairy black holes exist for all charges and
merge with the known CLP black holes along their superradiant onset curve. The
lowest mass hairy black hole is a smooth supersymmetric zero entropy soliton.
Together with the known phases of the truncation with three equal charges, our
findings permit a good understanding of the full phase space of SYM thermal
states with three arbitrary chemical potentials.Comment: 117 pages, 17 figure
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New symmetries of massless QED
An infinite number of physically nontrivial symmetries are found for abelian gauge theories with massless charged particles. They are generated by large U(1) gauge transformations that asymptotically approach an arbitrary function ε(z,z¯) on the conformal sphere at future null infinity (ℐ+) but are independent of the retarded time. The value of ε at past null infinity (ℐ−) is determined from that on ℐ+ by the condition that it take the same value at either end of any light ray crossing Minkowski space. The ε≠ constant symmetries are spontaneously broken in the usual vacuum. The associated Goldstone modes are zero-momentum photons and comprise a U(1) boson living on the conformal sphere. The Ward identity associated with this asymptotic symmetry is shown to be the abelian soft photon theorem.Physic
BMS supertranslations and Weinberg’s soft graviton theorem
Recently it was conjectured that a certain infinite-dimensional “diagonal” subgroup of BMS supertranslations acting on past and future null infinity (I − and I +) is an exact symmetry of the quantum gravity S-matrix, and an associated Ward identity was derived. In this paper we show that this supertranslation Ward identity is precisely equivalent to Weinberg’s soft graviton theorem. Along the way we construct the canonical generators of supertranslations at I ±, including the relevant soft graviton contributions. Boundary conditions at the past and future of I ± and a correspondingly modified Dirac bracket are required. The soft gravitons enter as boundary modes and are manifestly the Goldstone bosons of spontaneously broken supertranslation invariance.Physic