2,870 research outputs found
Dark Matter In Minimal Trinification
We study an example of Grand Unified Theory (GUT), known as trinification,
which was first introduced in 1984 by S.Glashow. This model has the GUT gauge
group as with a discrete to ensure the couplings are
unified at the GUT scale. In this letter we consider this trinification model
in its minimal formulation and investigate its robustness in the context of
cosmology. In particular we show that for a large set of the parameter space
the model doesn't seem to provide a Dark Matter candidate compatible with
cosmological data.Comment: To appear in the LXXXVI session of the "Les Houches" summer school. 9
pages, 2 graph
Worldline Green Functions for Arbitrary Feynman Diagrams
We propose a general method to obtain the scalar worldline Green function on
an arbitrary 1D topological space, with which the first-quantized method of
evaluating 1-loop Feynman diagrams can be generalized to calculate arbitrary
ones. The electric analog of the worldline Green function problem is found and
a compact expression for the worldline Green function is given, which has
similar structure to the 2D bosonic Green function of the closed bosonic
string.Comment: 20 pages, 6 figures; v2: typos corrected, references adde
Feynman rules for string field theories with discrete target space
We derive a minimal set of Feynman rules for the loop amplitudes in unitary
models of closed strings, whose target space is a simply laced (extended)
Dynkin diagram. The string field Feynman graphs are composed of propagators,
vertices (including tadpoles) of all topologies, and leg factors for the
macroscopic loops. A vertex of given topology factorizes into a fusion
coefficient for the matter fields and an intersection number associated with
the corresponding punctured surface. As illustration we obtain explicit
expressions for the genus-one tadpole and the genus-zero four-loop amplitude.Comment: 19 pages, harvmac, 4 uuencoded figures included using epsf. A missing
term added to the expression for the genus-one tadpole and Fig.3 modified
correspondingl
Integration-by-parts identities in FDR
Four-dimensional renormalized (FDR) integrals play an increasingly important
role in perturbative loop calculations. Thanks to them, loop computations can
be performed directly in four dimensions and with no ultraviolet (UV)
counterterms. In this paper I prove that integration-by-parts (IBP) identities
can be used to find relations among multi-loop FDR integrals. Since algorithms
based on IBP are widely applied beyond one loop, this result represents a
decisive step forward towards the use of FDR in multi-loop calculations.Comment: 13 page
Effective Superstrings
We generalize the method of quantizing effective strings proposed by
Polchinski and Strominger to superstrings. The Ramond-Neveu-Schwarz string is
different from the Green-Schwarz string in non-critical dimensions. Both are
anomaly-free and Poincare invariant. Some implications of the results are
discussed. The formal analogy with 4D (super)gravity is pointed out.Comment: 17 pages (including the title page
Vacuum Instability in Topologically Massive Gauge Theory
We find the critical charge for a topologically massive gauge theory for any
gauge group, generalising our earlier result for SU(2). The relation between
critical charges in TMGT, singular vectors in the WZNW model and logarithmic
CFT is investigated.Comment: 14 pages, Late
The anomaly in the central charge of the supersymmetric kink from dimensional regularization and reduction
We show that the anomalous contribution to the central charge of the
1+1-dimensional N=1 supersymmetric kink that is required for BPS saturation at
the quantum level can be linked to an analogous term in the extra momentum
operator of a 2+1-dimensional kink domain wall with spontaneous parity
violation and chiral domain wall fermions. In the quantization of the domain
wall, BPS saturation is preserved by nonvanishing quantum corrections to the
momentum density in the extra space dimension. Dimensional reduction from 2+1
to 1+1 dimensions preserves the unbroken N=1/2 supersymmetry and turns these
parity-violating contributions into the anomaly of the central charge of the
supersymmetric kink. On the other hand, standard dimensional regularization by
dimensional reduction from 1 to (1-epsilon) spatial dimensions, which also
preserves supersymmetry, obtains the anomaly from an evanescent counterterm.Comment: LATeX, 19 pages, v2: significantly extended section 4 on dimensional
reduction and evanescent counterterm
Superconformal theories from Pseudoparticle Mechanics
We consider a one-dimensional Osp() pseudoparticle mechanical model
which may be written as a phase space gauge theory. We show how the
pseudoparticle model naturally encodes and explains the two-dimensional zero
curvature approach to finding extended conformal symmetries. We describe a
procedure of partial gauge fixing of these theories which leads generally to
theories with superconformally extended -algebras. The pseudoparticle
model allows one to derive the finite transformations of the gauge and matter
fields occurring in these theories with extended conformal symmetries. In
particular, the partial gauge fixing of the Osp() pseudoparticle
mechanical models results in theories with the SO() invariant -extended
superconformal symmetry algebra of Bershadsky and Knizhnik. These algebras are
nonlinear for We discuss in detail the cases of and
giving two new derivations of the superschwarzian derivatives. Some comments
are made in the case on how twisted and topological theories represent a
significant deformation of the original particle model. The particle model also
allows one to interpret superconformal transformations as deformations of flags
in super jet bundles over the associated super Riemann surface.Comment: 36 pages, UTTG-93-00
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