6,288 research outputs found
The Origin of Space-Time as Symmetry Breaking in String Theory
Physics in the neighbourhood of a space-time metric singularity is described
by a world-sheet topological gauge field theory which can be represented as a
twisted superconformal Wess-Zumino model with a bosonic symmetry. The measurable -hair associated with the
singularity is associated with Wilson loop integrals around gauge defects. The
breaking of
is associated with expectation values for open Wilson lines that
make the metric non-singular away from the singularity. This symmetry breaking
is accompanied by massless discrete `tachyon' states that appear as leg poles
in -matrix elements. The triviality of the -matrix in the high-energy
limit of the string model, after renormalisation by the leg pole factors,
is due to the restoration of double -symmetry at the singularity.Comment: 13 page
Observation of acoustic spatiotemporal vortices
Vortices in fluids and gases have piqued the interest of human for centuries.
Development of classical-wave physics and quantum mechanics highlighted wave
vortices characterized by phase singularities and topological charges. In
particular, vortex beams have found numerous applications in modern optics and
other areas. Recently, optical spatiotemporal vortex states exhibiting the
phase singularity both in space and time have been reported. Here, we report
the first generation of acoustic spatiotemporal vortex pulses. We utilize an
acoustic meta-grating with mirror-symmetry breaking as the spatiotemporal
vortex generator. In the momentum-frequency domain, we unravel that the
transmission spectrum functions exhibit a topological phase transition where
the vortices with opposite topological charges are created or annihilated in
pairs. Furthermore, with the topological textures of the nodal lines, these
vortices are robust and exploited to generate spatiotemporal vortex pulse
against structural perturbations and disorder. Our work paves the way for
studies and applications of spatiotemporal structured waves in acoustics and
other wave systems.Comment: 12 pages, 4 figure
Short distance singularities and automatic O() improvement: the cases of the chiral condensate and the topological susceptibility
Short-distance singularities in lattice correlators can modify their Symanzik
expansion by leading to additional O() lattice artifacts. At the example of
the chiral condensate and the topological susceptibility, we show how to
account for these lattice artifacts for Wilson twisted mass fermions and show
that the property of automatic O() improvement is preserved at maximal
twist.Comment: 12 pages, corrected proof for topological susceptibility, version
published in JHE
Topological conditions for discrete symmetry breaking and phase transitions
In the framework of a recently proposed topological approach to phase
transitions, some sufficient conditions ensuring the presence of the
spontaneous breaking of a Z_2 symmetry and of a symmetry-breaking phase
transition are introduced and discussed. A very simple model, which we refer to
as the hypercubic model, is introduced and solved. The main purpose of this
model is that of illustrating the content of the sufficient conditions, but it
is interesting also in itself due to its simplicity. Then some mean-field
models already known in the literature are discussed in the light of the
sufficient conditions introduced here
A topological charge selection rule for phase singularities
We present an study of the dynamics and decay pattern of phase singularities
due to the action of a system with a discrete rotational symmetry of finite
order. A topological charge conservation rule is identified. The role played by
the underlying symmetry is emphasized. An effective model describing the short
range dynamics of the vortex clusters has been designed. A method to engineer
any desired configuration of clusters of phase singularities is proposed. Its
flexibility to create and control clusters of vortices is discussed.Comment: 4 pages, 3 figure
Duality in twisted N=4 supersymmetric gauge theories in four dimensions
We consider a twisted version of the four-dimensional N=4 supersymmetric
Yang-Mills theory with gauge groups SU(2) and SO(3), and bare masses for two of
its chiral multiplets, thereby breaking N=4 down to N=2. Using the
wall-crossing technique introduced by Moore and Witten within the u-plane
approach to twisted topological field theories, we compute the partition
function and all the topological correlation functions for the case of
simply-connected spin four-manifolds of simple type. By including 't Hooft
fluxes, we analyse the properties of the resulting formulae under duality
transformations. The partition function transforms in the same way as the one
first presented by Vafa and Witten for another twist of the N=4 supersymmetric
theory in their strong coupling test of S-duality. Both partition functions
coincide on K3. The topological correlation functions turn out to transform
covariantly under duality, following a simple pattern which seems to be
inherent in a general type of topological quantum field theories.Comment: 60 pages, phyzz
Supersymmetric Large Extra Dimensions and the Cosmological Constant Problem
This article briefly summarizes and reviews the motivations for - and the
present status of - the proposal that the small size of the observed Dark
Energy density can be understood in terms of the dynamical relaxation of two
large extra dimensions within a supersymmetric higher-dimensional theory.Comment: Talk presented to Theory Canada I, Vancouver, June 2005. References
added in V
The semi-classical expansion and resurgence in gauge theories: new perturbative, instanton, bion, and renormalon effects
We study the dynamics of four dimensional gauge theories with adjoint
fermions for all gauge groups, both in perturbation theory and
non-perturbatively, by using circle compactification with periodic boundary
conditions for the fermions. There are new gauge phenomena. We show that, to
all orders in perturbation theory, many gauge groups are Higgsed by the gauge
holonomy around the circle to a product of both abelian and nonabelian gauge
group factors. Non-perturbatively there are monopole-instantons with fermion
zero modes and two types of monopole-anti-monopole molecules, called bions. One
type are "magnetic bions" which carry net magnetic charge and induce a mass gap
for gauge fluctuations. Another type are "neutral bions" which are magnetically
neutral, and their understanding requires a generalization of multi-instanton
techniques in quantum mechanics - which we refer to as the
Bogomolny-Zinn-Justin (BZJ) prescription - to compactified field theory. The
BZJ prescription applied to bion-anti-bion topological molecules predicts a
singularity on the positive real axis of the Borel plane (i.e., a divergence
from summing large orders in peturbation theory) which is of order N times
closer to the origin than the leading 4-d BPST instanton-anti-instanton
singularity, where N is the rank of the gauge group. The position of the
bion--anti-bion singularity is thus qualitatively similar to that of the 4-d IR
renormalon singularity, and we conjecture that they are continuously related as
the compactification radius is changed. By making use of transseries and
Ecalle's resurgence theory we argue that a non-perturbative continuum
definition of a class of field theories which admit semi-classical expansions
may be possible.Comment: 112 pages, 7 figures; v2: typos corrected, discussion of
supersymmetric models added at the end of section 8.1, reference adde
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