58 research outputs found
Nonabelian Fields in Exact String Solutions
Within the framework of "anomalously gauged" Wess-Zumino-Witten (WZW) models,
we construct solutions which include nonabelian fields. Both compact and
noncompact groups are discussed. In the case of compact groups, as an example
of background containing nonabelian fields, we discuss conformal theory on the
coset, which is the natural generalization of the 2D monopole
theory corresponding to the coset. In noncompact case, we
consider examples with and cosets.Comment: 15 pages, Late
Quantum field theory with a fundamental length: A general mathematical framework
We review and develop a mathematical framework for nonlocal quantum field
theory (QFT) with a fundamental length. As an instructive example, we reexamine
the normal ordered Gaussian function of a free field and find the primitive
analyticity domain of its n-point vacuum expectation values. This domain is
smaller than the usual future tube of local QFT, but we prove that in
difference variables, it has the same structure of a tube whose base is the
(n-1)-fold product of a Lorentz invariant region. It follows that this model
satisfies Wightman-type axioms with an exponential high-energy bound which does
not depend on n, contrary to the claims in the literature. In our setting, the
Wightman generalized functions are defined on test functions analytic in the
complex l-neighborhood of the real space, where l is an n-independent constant
playing the role of a fundamental length, and the causality condition is
formulated with the use of an analogous function space associated with the
light cone. In contrast to the scheme proposed by Bruning and Nagamachi [J.
Math. Phys. 45 (2004) 2199] in terms of ultra-hyperfunctions, the presented
theory obviously becomes local as l tends to zero.Comment: 25 pages, v2: updated to match J. Math. Phys. versio
String-Loop Corrected Magnetic Black Holes
We discuss the form of the string-loop-corrected effective action obtained by
compactification of the heterotic string theory on the manifold
or on its orbifold limit and the loop-corrected magnetic black hole solutions
of the equations of motion. Effective 4D theory has N=2 local supersymmetry.
Using the string-loop-corrected prepotential of the N=2 supersymmetric theory,
which receives corrections only from the string world sheets of torus topology,
we calculate the loop corrections to the tree-level gauge couplings and solve
the loop-corrected equations of motion. At the string-tree level, the effective
gauge couplings decrease at small distances from the origin, and in this region
string-loop corrections to the gauge couplings become important. A possibility
of smearing the singularity of the tree-level supersymmetric solution with
partially broken supersymmetry by quantum corrections is discussed.Comment: Improved version. Mixing of the dilaton with other moduli properly
taken into account. Explanatory notes adde
Reconstruction in quantum field theory with a fundamental length
In this paper, we establish an analog of Wightman's reconstruction theorem
for nonlocal quantum field theory with a fundamental length. In our setting,
the Wightman generalized functions are defined on test functions analytic in a
complex l-neighborhood of the real space and are localizable at scales large
compared to l. The causality condition is formulated as continuity of the field
commutator in an appropriate topology associated with the light cone. We prove
that the relevant function spaces are nuclear and derive the kernel theorems
for the corresponding classes of multilinear functionals, which provides the
basis for the reconstruction procedure. Special attention is given to the
accurate determination of the domain of the reconstructed quantum fields in the
Hilbert space of states. We show that the primitive common invariant domain
must be suitably extended to implement the (quasi)localizability and causality
conditions.Comment: LaTeX, 23 pages, no figure
Infrared Properties of QCD from Dyson-Schwinger equations
I review recent results on the infrared properties of QCD from
Dyson-Schwinger equations. The topics include infrared exponents of
one-particle irreducible Green's functions, the fixed point behaviour of the
running coupling at zero momentum, the pattern of dynamical quark mass
generation and properties of light mesons.Comment: 47 pages, 19 figures, Topical Review to be published in J.Phys.G, v2:
typos corrected and some references adde
Supersymmetric Yang--Mills theories with exact supersymmetry on the lattice
Inspired by the ideas from topological field theory it is possible to rewrite
the supersymmetric charges of certain classes of extended supersymmetric
Yang--Mills (SYM) theories in such a way that they are compatible with the
discretization on a Euclidean spacetime lattice. Such theories are known as
maximally twisted SYM theories. In this review we discuss the construction and
some applications of such classes of theories. The one-loop perturbative
renormalization of the four-dimensional lattice SYM is discussed
in particular. The lattice theories constructed using twisted approach play an
important role in investigating the thermal phases of strongly coupled SYM
theories and also the thermodynamic properties of their dual gravitational
theories.Comment: 74 pages, 15 figures, minor revision, references added, published
versio
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