41 research outputs found
More on the Tensorial Central Charges in N=1 Supersymmetric Gauge Theories (BPS Wall Junctions and Strings)
We study the central extensions of the N=1 superalgebras relevant to the
soliton solutions with the axial geometry - strings, wall junctions, etc. A
general expression valid in any four-dimensional gauge theory is obtained. We
prove that the only gauge theory admitting BPS strings at weak coupling is
supersymmetric electrodynamics with the Fayet-Iliopoulos term. The problem of
ambiguity of the (1/2,1/2) central charge in the generalized Wess-Zumino models
and gauge theories with matter is addressed and solved. A possibility of
existence of the BPS strings at strong coupling in N=2 theories is discussed. A
representation of different strings within the brane picture is presented.Comment: 26 pages, 2 figures, 1 reference added, typos corrected, Sec. 9.3
expanded. Final version accepted for publication in Phys.Rev.
Domain Wall Junction in N=2 Supersymmetric QED in four dimensions
An exact solution of domain wall junction is obtained in N=2 supersymmetric
(SUSY) QED with three massive hypermultiplets. The junction preserves two out
of eight SUSY. Both a (magnetic) Fayet-Iliopoulos (FI) term and complex masses
for hypermultiplets are needed to obtain the junction solution. There are zero
modes corresponding to spontaneously broken translation, SUSY, and U(1). All
broken and unbroken SUSY charges are explicitly worked out in the Wess-Zumino
gauge in N=1 superfields as well as in components. The relation to models in
five dimensions is also clarified.Comment: 27 pages, 6 figures, comments on zero modes added, a few references
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Generalized Global Defect Solutions
We investigate the presence of defect structures in generalized models
described by real scalar field in space-time dimensions. We work with
two distinct generalizations, one in the form of a product of functions of the
field and its derivative, and the other as a sum. We search for static
solutions and study the corresponding linear stability on general grounds. We
illustrate the results with several examples, where we find stable defect
structures of modified profile. In particular, we show how the new defect
solutions may give rise to evolutions not present in the standard scenario in
higher spatial dimensions.Comment: RevTex, 10 pages, 2 figures; version to appear in EPJ
Solvable Models of Domain Walls in N=1 Supergravity
A class of exactly solvable models of domain walls are worked out in D=4
supergravity. We develop a method to embed globally supersymmetric
theories with exact BPS domain wall solutions into supergravity, by introducing
a gravitationally deformed superpotential. The gravitational deformation is
natural in the spirit of maintaining the K\"ahler invariance. The solutions of
the warp factor and the Killing spinor are also obtained. We find that three
distinct behaviors of warp factors arise depending on the value of a constant
term in the superpotential : exponentially decreasing in both sides of the
wall, flat in one side and decreasing in the other, and increasing in one side
and decreasing in the other. Only the first possibility gives the localized
massless graviton zero mode. Models with multi-walls and models with runaway
vacua are also discussed.Comment: 10 pages, 3 figures; Misprints in three formulas are correcte
Categorizing Different Approaches to the Cosmological Constant Problem
We have found that proposals addressing the old cosmological constant problem
come in various categories. The aim of this paper is to identify as many
different, credible mechanisms as possible and to provide them with a code for
future reference. We find that they all can be classified into five different
schemes of which we indicate the advantages and drawbacks.
Besides, we add a new approach based on a symmetry principle mapping real to
imaginary spacetime.Comment: updated version, accepted for publicatio
Entrapment of a Network of Domain Walls
We explore the idea of a network of defects to live inside a domain wall in
models of three real scalar fields, engendering the Z_2 x Z_3 symmetry. The
field that governs the Z_2 symmetry generates a domain wall, and entraps the
hexagonal network formed by the three-junctions of the model of two scalar
fields that describes the remaining Z_3 symmetry. If the host domain wall bends
to the spherical form, in the thin wall approximation there may appear
non-topological structures hosting networks that accept diverse patterns. If
Z_3 is also broken, the model may generate a buckyball containing sixty
junctions, a fullerene-like structure. Applications to cosmology are outlined.Comment: Revtex, 4 pages, 2 ps figures; version to appear in Phys. Rev. D,
Rapid Communicatio
Human Health Risk Assessment For Arsenic: A Critical Review
Millions of people are exposed to arsenic resulting in a range of health implications.This paper provides an up-to-date review of the different sources of arsenic (water, soil and food), indicators of human exposure (biomarker assessment of hair, nail, urine and blood), epidemiological and toxicological studies on carcinogenic and non-carcinogenic health outcomes, and risk assessment approaches. The review demonstrates a need for more work evaluating the risks of different arsenic species such as; arsenate, arsenite monomethylarsonic acid, monomethylarsonous acid, dimethylarsinic acid and dimethylarsinous acid as well as a need to better integrate the different exposure sources in risk assessments
Transmission of Tuberculosis with Exogenous Re-infection and Endogenous Reactivation
A theoretical framework to assess the transmission dynamics of Tuberculosis (TB) is developed. Once infected with Mycobacterium tuberculosis, individuals can either develop active TB or remain infected for the rest of their life unless endogenous reactivation or exogenous re-infection occurs. The effects of vaccination and treatment of active TB cases suggest that even if these control strategies could have a significant effect on reducing TB incidence, the exogenous re-infection and the endogenous reactivation, mainly due to HIV infection, will still increase the incidence of TB.endogenous reactivation, exogenous re-infection, mathematical modeling, Mycobacterium tuberculosis ,