17,003 research outputs found
Nonsingular 4d-flat branes in six-dimensional supergravities
We show that six-dimensional supergravity models admit nonsingular solutions
in the presence of flat three-brane sources with positive tensions. The models
studied in this paper are nonlinear sigma models with the target spaces of the
scalar fields being noncompact manifolds. For the particular solutions of the
scalar field equations which we consider, only two brane sources are possible
which are positioned at those points where the scalar field densities diverge,
without creating a divergence in the Ricci scalar or the total energy. These
solutions are locally invariant under 1/2 of D=6 supersymmetries, which,
however, do not integrate to global Killing spinors. Other branes can be
introduced by hand by allowing for local deficit angles in the transverse space
without generating any kind of curvature singularities.Comment: 13 pages. The discussion of modular invariance is amended and a
reference has been adde
Solitons in a six-dimensional super Yang-Mills-tensor system and noncritical strings
In this letter we study a coupled system of six-dimensional N=1 tensor and
super Yang-Mills multiplets. We identify some of the solitonic states of this
system which exhibit stringy behaviour in six dimensions. A discussion of the
supercharges and energy for the tensor multiplet as well as zero modes is also
given. We speculate about the possible relationship between our solution and
what is known as tensionless strings.Comment: Plain TeX, 10 page
Magnetic Field and Curvature Effects on Pair Production I: Scalars and Spinors
The pair production rates for spin-zero and spin- particles are
calculated on spaces of the form with
corresponding to (flat), (flat, compactified),
(positive curvature) and (negative curvature), with and without a
background magnetic field on . The motivation is to elucidate the effects of
curvature and background magnetic field. Contrasting effects for positive and
negative curvature on the two cases of spin are obtained. For positive
curvature, we find enhancement for spin-zero and suppression for
spin-, with the opposite effect for negative curvature.Comment: 28 pages, 10 figure
Magnetic Field and Curvature Effects on Pair Production II: Vectors and Implications for Chromodynamics
We calculate the pair production rates for spin- or vector particles on
spaces of the form with corresponding to
(flat), (positive curvature) and (negative
curvature), with and without a background (chromo)magnetic field on . Beyond
highlighting the effects of curvature and background magnetic field, this is
particularly interesting since vector particles are known to suffer from the
Nielsen-Olesen instability, which can dramatically increase pair production
rates. The form of this instability for and is obtained. We also
give a brief discussion of how our results relate to ideas about confinement in
nonabelian theories.Comment: 24 pages, 9 figure
Recommended from our members
Trust Model for Optimized Cloud Services
Cloud computing with its inherent advantages draws attention for business critical applications, but concurrently expects high level of trust in cloud service providers. Reputation-based trust is emerging as a good choice to model trust of cloud service providers based on available evidence. Many existing reputation based systems either ignore or give less importance to uncertainty linked with the evidence. In this paper, we propose an uncertainty model and define our approach to compute opinion for cloud service providers. Using subjective logic operators along with the computed opinion values, we propose mechanisms to calculate the reputation of cloud service providers. We evaluate and compare our proposed model with existing reputation models
On Level Quantization for the Noncommutative Chern-Simons Theory
We show that the coefficient of the three-dimensional Chern-Simons action on
the noncommutative plane must be quantized. Similar considerations apply in
other dimensions as well.Comment: 6 pages, Latex, no figure
A Note on Schwinger Mechanism and a Nonabelian Instability in a Nonabelian Plasma
We point out that there is a nonabelian instability for a nonabelian plasma
which does not allow both for a net nonzero color charge and the existence of
field configurations which are coherent over a volume whose size is
determined by the chemical potential. The basic process which leads to this
result is the Schwinger decay of chromoelectric fields, for the case where the
field arises from commutators of constant potentials, rather than as the curl
of spacetime dependent potentials. In terms of the fields, instability is
obtained when Tr(DF)^2 > 0.Comment: 14 pages, 6 figure
Hepatitis B Associated Monoclonal Gammopathy That Resolved after Successful Liver Transplant
Monoclonal gammopathy of undetermined significance (MGUS) has been most commonly associated with diseases like multiple myeloma, Waldenstrom's macroglobulinemia, primary systemic amyloidosis, HIV, and other lymphoproliferative disorders. There has been an isolated report of MGUS in patients coinfected with HIV and Hepatitis B, as the work by Amara et al. in 2006. Here, we report a case of IgA-kappa light chain gammopathy secondary to Hepatitis B infection, which resolved after liver transplantation. To our knowledge, this is the first reported case of M protein spike seen in the context of Hepatitis B infection only
- …