114 research outputs found
Gravitational Chern-Simons and the adiabatic limit
We compute the gravitational Chern-Simons term explicitly for an adiabatic
family of metrics using standard methods in general relativity. We use the fact
that our base three-manifold is a quasi-regular K-contact manifold heavily in
this computation. Our key observation is that this geometric assumption
corresponds exactly to a Kaluza-Klein Ansatz for the metric tensor on our three
manifold, which allows us to translate our problem into the language of general
relativity. Similar computations have been performed in a paper of Guralnik,
Iorio, Jackiw and Pi (2003), although not in the adiabatic context.Comment: 17 page
Yang-Mills mass gap at large-N, non-commutative YM theory, topological quantum field theory and hyperfiniteness
We review a number of old and new concepts in quantum gauge theories, some of
which are well established but not widely appreciated, some are most recent.
Such concepts involve non-commutative gauge theories and their relation to the
large-N limit, loop equations and the change to the anti-selfdual variables
also known as Nicolai map, topological field theory (TFT) and its relation to
localization and Morse-Smale-Floer homology, with an emphasis both on the
mathematical aspects and the physical meaning. These concepts, assembled in a
new way, enter a line of attack to the problem of the mass gap in large-N SU(N)
YM, that is reviewed as well. In the large-N limit of pure SU(N) YM the ambient
algebra of Wilson loops is known to be a type II_1 non-hyperfinite factor.
Nevertheless, for the mass gap problem at the leading 1/N order, only the
subalgebra of local gauge-invariant single-trace operators matters. The
connected two-point correlators in this subalgebra must be an infinite sum of
propagators of free massive fields, a vast simplification. It is an open
problem, determined by the grow of the degeneracy of the spectrum, whether the
aforementioned local subalgebra is in fact hyperfinite. For the mass-gap
problem, in the search of a hyperfinite subalgebra containing the scalar sector
of large-N YM, a major role is played by the existence of a TFT underlying the
large-N limit of YM, with twisted boundary conditions on a torus or, what is
the same by Morita duality, on a non-commutative torus.Comment: 19 pages, latex; the paper, originally a byproduct of the workshop:
Mathematical Foundations of Quantum Field Theory, Jan 16-20 (2012), has been
expanded and rewritten as a short review in order to include most recent
developments. To appear in IJMP
A sub-product construction of Poincare-Einstein metrics
Given any two Einstein (pseudo-)metrics, with scalar curvatures suitably
related, we give an explicit construction of a Poincar\'e-Einstein
(pseudo-)metric with conformal infinity the conformal class of the product of
the initial metrics. We show that these metrics are equivalent to ambient
metrics for the given conformal structure. The ambient metrics have holonomy
that agrees with the conformal holonomy. In the generic case the ambient metric
arises directly as a product of the metric cones over the original Einstein
spaces. In general the conformal infinity of the Poincare metrics we construct
is not Einstein, and so this describes a class of non-conformally Einstein
metrics for which the (Fefferman-Graham) obstruction tensor vanishes.Comment: 23 pages Minor correction to section 5. References update
Stability and Hermitian-Einstein metrics for vector bundles on framed manifolds
We adapt the notions of stability of holomorphic vector bundles in the sense
of Mumford-Takemoto and Hermitian-Einstein metrics in holomorphic vector
bundles for canonically polarized framed manifolds, i.e. compact complex
manifolds X together with a smooth divisor D such that K_X \otimes [D] is
ample. It turns out that the degree of a torsion-free coherent sheaf on X with
respect to the polarization K_X \otimes [D] coincides with the degree with
respect to the complete K\"ahler-Einstein metric g_{X \setminus D} on X
\setminus D. For stable holomorphic vector bundles, we prove the existence of a
Hermitian-Einstein metric with respect to g_{X \setminus D} and also the
uniqueness in an adapted sense.Comment: 21 pages, International Journal of Mathematics (to appear
Remarks on evolution of space-times in 3+1 and 4+1 dimensions
A large class of vacuum space-times is constructed in dimension 4+1 from
hyperboloidal initial data sets which are not small perturbations of empty
space data. These space-times are future geodesically complete, smooth up to
their future null infinity, and extend as vacuum space-times through their
Cauchy horizon. Dimensional reduction gives non-vacuum space-times with the
same properties in 3+1 dimensions.Comment: 10pp, exposition improved; final versio
A Kummer construction for gravitational instantons
We give a simple and uniform construction of essentially all known
deformation classes of gravitational instantons with ALF, ALG or ALH
asymptotics and nonzero injectivity radius. We also construct new ALH Ricci
flat metrics asymptotic to the product of a real line with a flat 3-manifold.Comment: The construction of locally hyperkahler ALH spaces is corrected and
complete
Chiral formulation for hyperkaehler sigma-models on cotangent bundles of symmetric spaces
Starting with the projective-superspace off-shell formulation for
four-dimensional N = 2 supersymmetric sigma-models on cotangent bundles of
arbitrary Hermitian symmetric spaces, their on-shell description in terms of N
= 1 chiral superfields is developed. In particular, we derive a universal
representation for the hyperkaehler potential in terms of the curvature of the
symmetric base space. Within the tangent-bundle formulation for such
sigma-models, completed recently in arXiv:0709.2633 and realized in terms of N
= 1 chiral and complex linear superfields, we give a new universal formula for
the superspace Lagrangian. A closed form expression is also derived for the
Kaehler potential of an arbitrary Hermitian symmetric space in Kaehler normal
coordinates.Comment: 11 pages, LaTeX, no figue
Exact beta function from the holographic loop equation of large-N QCD_4
We construct and study a previously defined quantum holographic effective
action whose critical equation implies the holographic loop equation of large-N
QCD_4 for planar self-avoiding loops in a certain regularization scheme. We
extract from the effective action the exact beta function in the given scheme.
For the Wilsonean coupling constant the beta function is exacly one loop and
the first coefficient agrees with its value in perturbation theory. For the
canonical coupling constant the exact beta function has a NSVZ form and the
first two coefficients agree with their value in perturbation theory.Comment: 42 pages, latex. The exponent of the Vandermonde determinant in the
quantum effective action has been changed, because it has been employed a
holomorphic rather than a hermitean resolution of identity in the functional
integral. Beta function unchanged. New explanations and references added,
typos correcte
Fourier-Laplace transform of a variation of polarized complex Hodge structure, II
We show that the limit, by rescaling, of the `new supersymmetric index'
attached to the Fourier-Laplace transform of a polarized variation of Hodge
structure on a punctured affine line is equal to the spectral polynomial
attached to the same object. We also extend the definition by Deligne of a
Hodge filtration on the de Rham cohomology of a exponentially twisted polarized
variation of complex Hodge structure and prove a E_1 degeneration property for
it.Comment: 51 pages, revised version, to appear in the proceedings volume of the
conference `` New developments in Algebraic Geometry, Integrable Systems and
Mirror symmetry", RIMS, Kyoto, Jan. 7-11, 200
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