6,117 research outputs found
On Representations of Conformal Field Theories and the Construction of Orbifolds
We consider representations of meromorphic bosonic chiral conformal field
theories, and demonstrate that such a representation is completely specified by
a state within the theory. The necessary and sufficient conditions upon this
state are derived, and, because of their form, we show that we may extend the
representation to a representation of a suitable larger conformal field theory.
In particular, we apply this procedure to the lattice (FKS) conformal field
theories, and deduce that Dong's proof of the uniqueness of the twisted
representation for the reflection-twisted projection of the Leech lattice
conformal field theory generalises to an arbitrary even (self-dual) lattice. As
a consequence, we see that the reflection-twisted lattice theories of Dolan et
al are truly self-dual, extending the analogies with the theories of lattices
and codes which were being pursued. Some comments are also made on the general
concept of the definition of an orbifold of a conformal field theory in
relation to this point of view.Comment: 11 pages, LaTeX. Updated references and added preprint n
Quantum fluctuations of the electroweak sphaleron: Erratum and Addendum
We correct an error in our treatment of the tadpole contribution to the
fluctuation determinant of the sphaleron, and also a minor mistake in a
previous estimate. Thereby the overall agreement between the two existing exact
computations and their consistency with the estimate is improved considerably.Comment: 4 pages, Dortmund preprint DO-TH-93/19E
Effective Action of Spontaneously Broken Gauge Theories
The effective action of a Higgs theory should be gauge-invariant. However,
the quantum and/or thermal contributions to the effective potential seem to be
gauge-dependent, posing a problem for its physical interpretation. In this
paper, we identify the source of the problem and argue that in a Higgs theory,
perturbative contributions should be evaluated with the Higgs fields in the
polar basis, not in the Cartesian basis. Formally, this observation can be made
from the derivation of the Higgs theorem, which we provide. We show explicitly
that, properly defined, the effective action for the Abelian Higgs theory is
gauge invariant to all orders in perturbation expansion when evaluated in the
covariant gauge in the polar basis. In particular, the effective potential is
gauge invariant. We also show the equivalence between the calculations in the
covariant gauge in the polar basis and the unitary gauge. These points are
illustrated explicitly with the one-loop calculations of the effective action.
With a field redefinition, we obtain the physical effective potential. The
SU(2) non-Abelian case is also discussed.Comment: Expanded version, 32 pages, figures produced by LaTeX, plain LaTe
To BrAIST or not to BrAIST: decisions and characteristics of 1131 patients eligible for the Bracing in Adolescent Idiopathic Scoliosis Trial
On the Role of Chaos in the AdS/CFT Connection
The question of how infalling matter in a pure state forms a Schwarzschild
black hole that appears to be at non-zero temperature is discussed in the
context of the AdS/CFT connection. It is argued that the phenomenon of
self-thermalization in non-linear (chaotic) systems can be invoked to explain
how the boundary theory, initially at zero temperature self thermalizes and
acquires a finite temperature. Yang-Mills theory is known to be chaotic
(classically) and the imaginary part of the gluon self-energy (damping rate of
the gluon plasma) is expected to give the Lyapunov exponent. We explain how the
imaginary part would arise in the corresponding supergravity calculation due to
absorption at the horizon of the black hole.Comment: 18 pages. Latex file. Minor changes. Final version to appear in
Modern Physics Letters
Higher-dimensional Algebra and Topological Quantum Field Theory
The study of topological quantum field theories increasingly relies upon
concepts from higher-dimensional algebra such as n-categories and n-vector
spaces. We review progress towards a definition of n-category suited for this
purpose, and outline a program in which n-dimensional TQFTs are to be described
as n-category representations. First we describe a "suspension" operation on
n-categories, and hypothesize that the k-fold suspension of a weak n-category
stabilizes for k >= n+2. We give evidence for this hypothesis and describe its
relation to stable homotopy theory. We then propose a description of
n-dimensional unitary extended TQFTs as weak n-functors from the "free stable
weak n-category with duals on one object" to the n-category of "n-Hilbert
spaces". We conclude by describing n-categorical generalizations of deformation
quantization and the quantum double construction.Comment: 36 pages, LaTeX; this version includes all 36 figure
Equivalence between Kaluza Klein modes of gravitinos and goldstinos in brane induced supersymmetry breaking
We identify the goldstino fields that give mass to the Kaluza Klein modes of
five dimensional supergravity, when supersymmetry breaking is induced by brane
effects. We then proof the four dimensional Equivalence Theorem that, in
renormalizable gauges, allows for the replacement of Kaluza Klein modes of
helicity gravitinos in terms of goldstinos. Finally we identify the
five dimensional renormalizable gauge fixing that leads to the Equivalence
Theorem.Comment: Final version published in JHEP. Typo corrected in eq. 2.
Anomalous dimension and local charges
AdS space is the universal covering of a hyperboloid. We consider the action
of the deck transformations on a classical string worldsheet in . We argue that these transformations are generated by an infinite linear
combination of the local conserved charges. We conjecture that a similar
relation holds for the corresponding operators on the field theory side. This
would be a generalization of the recent field theory results showing that the
one loop anomalous dimension is proportional to the Casimir operator in the
representation of the Yangian algebra.Comment: 10 pages, LaTeX; v2: added explanations, reference
Persistent pain after caesarean section and its association with maternal anxiety and socioeconomic background
Background:
Pain, both from the surgical site, and from other sources such as musculoskeletal backache, can persist after caesarean section. In this study of a predominantly socially deprived population we have sought to prospectively examine the association between antenatal maternal anxiety and socioeconomic background and the development of persistent pain of all sources after caesarean section.
Methods:
Demographic details and an anxiety questionnaire were completed by 205 women before elective caesarean section. On the first postoperative day, pain scores were recorded, and at four months patients were asked to complete a Brief Pain Inventory and an Edinburgh Postnatal Depression Score.
Results:
Of 205 parturients recruited, 186 records were complete at the hospital admission phase and 98 (52.7%) were complete at the four-month follow-up phase. At recruitment, 15.1% reported pain. At four months 41.8% (95% CI 32.1 to 51.6%) reported pain, of whom pain was a new finding in 35.7% (95% CI 26.2 to 45.2%). Antenatal anxiety was not a significant predictor of severity of new pain at four months (P=0.43 for state anxiety, P=0.52 for trait anxiety). However, four-month pain severity did correlate with social deprivation (P=0.011), postnatal depression (P<0.001) and pain at 24 h (P=0.018).
Conclusion:
Persistent pain from a variety of sources after caesarean section is common. Our findings do not support the use of antenatal anxiety scoring to predict persistent pain in this setting, but suggest that persistent pain is influenced by acute pain, postnatal depression and socioeconomic deprivation
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