857 research outputs found
Wilson Loop Renormalization Group Flows
The locally BPS Wilson loop and the pure gauge Wilson loop map under AdS/CFT
duality to string world-sheet boundaries with standard and alternate
quantizations of the world-sheet fields. This implies an RG flow between the
two operators, which we verify at weak coupling. Many additional loop operators
exist at strong coupling, with a rich pattern of RG flows.Comment: 10 p, 2 figures. v3: Title change, expanded treatment of RG flow
Loop expansion in Yang-Mills thermodynamics
We argue that a selfconsistent spatial coarse-graining, which involves
interacting (anti)calorons of unit topological charge modulus, implies that
real-time loop expansions of thermodynamical quantities in the deconfining
phase of SU(2) and SU(3) Yang-Mills thermodynamics are, modulo 1PI
resummations, determined by a finite number of connected bubble diagrams.Comment: 15 pages, 2 figures, v5: discussion of much more severely constrained
nonplanar situation included in Sec.
Effective String Theory and Nonlinear Lorentz Invariance
We study the low-energy effective action governing the transverse
fluctuations of a long string, such as a confining flux tube in QCD. We work in
the static gauge where this action contains only the transverse excitations of
the string. The static gauge action is strongly constrained by the requirement
that the Lorentz symmetry, that is spontaneously broken by the long string
vacuum, is nonlinearly realized on the Nambu-Goldstone bosons. One solution to
the constraints (at the classical level) is the Nambu-Goto action, and the
general solution contains higher derivative corrections to this. We show that
in 2+1 dimensions, the first allowed correction to the Nambu-Goto action is
proportional to the squared curvature of the induced metric on the worldsheet.
In higher dimensions, there is a more complicated allowed correction that
appears at lower order than the curvature squared. We argue that this leading
correction is similar to, but not identical to, the one-loop determinant
(\sqrt{-h} R \Box^{-1} R) computed by Polyakov for the bosonic fundamental
string.Comment: 15 page
Holographic Phase Transition to Topological Dyons
The dynamical stability of a Julia-Zee solution in the AdS background in a
four dimensional Einstein-Yang-Mills-Higgs theory is studied. We find that the
model with a vanishing scalar field develops a non-zero value for the field at
a certain critical temperature which corresponds to a topological dyon in the
bulk and a topological phase transition at the boundary.Comment: 18 pages, 2 figures, 2 tables, sections 2 and 4 are shortened, an
error in the last part of section 5 is corrected and equations are modified.
This version to be published in JHE
Diagonal deformations of thin center vortices and their stability in Yang-Mills theories
The importance of center vortices for the understanding of the confining
properties of SU(N) Yang-Mills theories is well established in the lattice.
However, in the continuum, there is a problem concerning the relevance of
center vortex backgrounds. They display the so called Savvidy-Nielsen-Olesen
instability, associated with a gyromagnetic ratio for the
off-diagonal gluons.
In this work, we initially consider the usual definition of a {\it thin}
center vortex and rewrite it in terms of a local color frame in SU(N)
Yang-Mills theories. Then, we define a thick center vortex as a diagonal
deformation of the thin object. Besides the usual thick background profile,
this deformation also contains a frame defect coupled with gyromagnetic ratio
, originated from the charged sector. As a consequence, the
analysis of stability is modified. In particular, we point out that the defect
should stabilize a vortex configuration formed by a pair of straight components
separated by an appropriate finite distance.Comment: 20 pages, LaTe
The effective string spectrum in the orthogonal gauge
The low-energy effective action on long string-like objects in quantum field
theory, such as confining strings, includes the Nambu-Goto action and then
higher-derivative corrections. This action is diffeomorphism-invariant, and can
be analyzed in various gauges. Polchinski and Strominger suggested a specific
way to analyze this effective action in the orthogonal gauge, in which the
induced metric on the worldsheet is conformally equivalent to a flat metric.
Their suggestion leads to a specific term at the next order beyond the
Nambu-Goto action. We compute the leading correction to the Nambu-Goto spectrum
using the action that includes this term, and we show that it agrees with the
leading correction previously computed in the static gauge. This gives a
consistency check for the framework of Polchinski and Strominger, and helps to
understand its relation to the theory in the static gauge.Comment: 21 page
Effective String Theory Revisited
We revisit the effective field theory of long relativistic strings such as
confining flux tubes in QCD. We derive the Polchinski-Strominger interaction by
a calculation in static gauge. This interaction implies that a non-critical
string which initially oscillates in one direction gets excited in orthogonal
directions as well. In static gauge no additional term in the effective action
is needed to obtain this effect. It results from a one-loop calculation using
the Nambu-Goto action. Non-linearly realized Lorentz symmetry is manifest at
all stages in dimensional regularization. We also explain that independent of
the number of dimensions non-covariant counterterms have to be added to the
action in the commonly used zeta-function regularization.Comment: 21 pages, 4 figures, v2: typo corrected, references added, published
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On the Perturbative Stability of Quantum Field Theories in de Sitter Space
We use a field theoretic generalization of the Wigner-Weisskopf method to
study the stability of the Bunch-Davies vacuum state for a massless,
conformally coupled interacting test field in de Sitter space. We find that in
theory the vacuum does {\em not} decay, while in
non-conformally invariant models, the vacuum decays as a consequence of a
vacuum wave function renormalization that depends \emph{singularly} on
(conformal) time and is proportional to the spatial volume. In a particular
regularization scheme the vacuum wave function renormalization is the same as
in Minkowski spacetime, but in terms of the \emph{physical volume}, which leads
to an interpretation of the decay. A simple example of the impact of vacuum
decay upon a non-gaussian correlation is discussed. Single particle excitations
also decay into two particle states, leading to particle production that
hastens the exiting of modes from the de Sitter horizon resulting in the
production of \emph{entangled superhorizon pairs} with a population consistent
with unitary evolution. We find a non-perturbative, self-consistent "screening"
mechanism that shuts off vacuum decay asymptotically, leading to a stationary
vacuum state in a manner not unlike the approach to a fixed point in the space
of states.Comment: 36 pages, 4 figures. Version to appear in JHEP, more explanation
Rectangular Wilson Loops at Large N
This work is about pure Yang-Mills theory in four Euclidean dimensions with
gauge group SU(N). We study rectangular smeared Wilson loops on the lattice at
large N and relatively close to the large-N transition point in their
eigenvalue density. We show that the string tension can be extracted from these
loops but their dependence on shape differs from the asymptotic prediction of
effective string theory.Comment: 47 pages, 21 figures, 8 table
Conformal invariance in two-dimensional turbulence
Simplicity of fundamental physical laws manifests itself in fundamental
symmetries. While systems with an infinity of strongly interacting degrees of
freedom (in particle physics and critical phenomena) are hard to describe, they
often demonstrate symmetries, in particular scale invariance. In two dimensions
(2d) locality often promotes scale invariance to a wider class of conformal
transformations which allow for nonuniform re-scaling. Conformal invariance
allows a thorough classification of universality classes of critical phenomena
in 2d. Is there conformal invariance in 2d turbulence, a paradigmatic example
of strongly-interacting non-equilibrium system? Here, using numerical
experiment, we show that some features of 2d inverse turbulent cascade display
conformal invariance. We observe that the statistics of vorticity clusters is
remarkably close to that of critical percolation, one of the simplest
universality classes of critical phenomena. These results represent a new step
in the unification of 2d physics within the framework of conformal symmetry.Comment: 10 pages, 5 figures, 1 tabl
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