18,119 research outputs found
New vector-scalar contributions to neutrinoless double beta decay and constraints on R-parity violation
We show that in minimal supersymmetric standard model (MSSM) with R-parity
breaking as well as in the left-right symmetric model, there are new observable
contributions to neutrinoless double beta decay arising from hitherto
overlooked diagrams involving the exchange of one W boson and one scalar boson.
In particular, in the case of MSSM, the present experimental bounds on
neutrinoless double beta decay lifetime improves the limits on certain R-parity
violating couplings by about two orders of magnitude. It is shown that similar
diagrams also lead to enhanced rates for conversion in
nuclei, which are in the range accessible to ongoing experiments.Comment: Latex file; 9 pages; 3 figures available on reques
How strong is the evidence for accelerated expansion?
We test the present expansion of the universe using supernova type Ia data
without making any assumptions about the matter and energy content of the
universe or about the parameterization of the deceleration parameter. We assume
the cosmological principle to apply in a strict sense. The result strongly
depends on the data set, the light-curve fitting method and the calibration of
the absolute magnitude used for the test, indicating strong systematic errors.
Nevertheless, in a spatially flat universe there is at least a 5 sigma evidence
for acceleration which drops to 1.8 sigma in an open universe.Comment: 16 pages, 3 figure
Calculating the Prepotential by Localization on the Moduli Space of Instantons
We describe a new technique for calculating instanton effects in
supersymmetric gauge theories applicable on the Higgs or Coulomb branches. In
these situations the instantons are constrained and a potential is generated on
the instanton moduli space. Due to existence of a nilpotent fermionic symmetry
the resulting integral over the instanton moduli space localizes on the
critical points of the potential. Using this technology we calculate the one-
and two-instanton contributions to the prepotential of SU(N) gauge theory with
N=2 supersymmetry and show how the localization approach yields the prediction
extracted from the Seiberg-Witten curve. The technique appears to extend to
arbitrary instanton number in a tractable way.Comment: 24 pages, JHEP.cls, more references and extra discussion on N_F=2N
cas
Zero-Mode Dynamics of String Webs
At sufficiently low energy the dynamics of a string web is dominated by zero
modes involving rigid motion of the internal strings. The dimension of the
associated moduli space equals the maximal number of internal faces in the web.
The generic web moduli space has boundaries and multiple branches, and for webs
with three or more faces the geometry is curved. Webs can also be studied in a
lift to M-theory, where a string web is replaced by a membrane wrapped on a
holomorphic curve in spacetime. In this case the moduli space is complexified
and admits a Kaehler metric.Comment: LaTeX, 17 pages, 5 eps figures; v2: references adde
Supersymmetric Gauge Theories with an Affine Quantum Moduli Space
All supersymmetric gauge theories based on simple groups which have an affine
quantum moduli space, i.e. one generated by gauge invariants with no relations,
W=0, and anomaly matching at the origin, are classified. It is shown that the
only theories with no gauge invariants (and moduli space equal to a single
point) are the two known examples, SU(5) with 5-bar + 10 and SO(10) with a
spinor. The index of the matter representation must be at least as big as the
index of the adjoint in theories which have a non-trivial relation among the
gauge invariants.Comment: Incorrect proof that theories with constraints must have mu >=
mu(adj) replaced by a correct one (6 pages, uses revtex, amssymb, array
Excitation of a Kaluza-Klein mode by parametric resonance
In this paper we investigate a parametric resonance phenomenon of a
Kaluza-Klein mode in a -dimensional generalized Kaluza-Klein theory. As the
origin of the parametric resonance we consider a small oscillation of a scale
of the compactification around a today's value of it. To make our arguments
definite and for simplicity we consider two classes of models of the
compactification: those by () and those by (, ). For these models we show that
parametric resonance can occur for the Kaluza-Klein mode. After that, we give
formulas of a creation rate and a number of created quanta of the Kaluza-Klein
mode due to the parametric resonance, taking into account the first and the
second resonance band. By using the formulas we calculate those quantities for
each model of the compactification. Finally we give conditions for the
parametric resonance to be efficient and discuss cosmological implications.Comment: 36 pages, Latex file, Accepted for publication in Physical Review
Dyons in N=4 Supersymmetric Theories and Three-Pronged Strings
We construct and explore BPS states that preserve 1/4 of supersymmetry in N=4
Yang-Mills theories. Such states are also realized as three-pronged strings
ending on D3-branes. We correct the electric part of the BPS equation and
relate its solutions to the unbroken abelian gauge group generators. Generic
1/4-BPS solitons are not spherically symmetric, but consist of two or more
dyonic components held apart by a delicate balance between static
electromagnetic force and scalar Higgs force. The instability previously found
in three-pronged string configurations is due to excessive repulsion by one of
these static forces. We also present an alternate construction of these 1/4-BPS
states from quantum excitations around a magnetic monopole, and build up the
supermultiplet for arbitrary (quantized) electric charge. The degeneracy and
the highest spin of the supermultiplet increase linearly with a relative
electric charge. We conclude with comments.Comment: 33 pages, two figures, LaTex, a footnote added, the figure caption of
Fig.2 expanded, one more referenc
Relating Spin Foams and Canonical Quantum Gravity: A Discrete Step Evolution Formulation of Spin Foams
This article has been replaced by gr-qc/0412011Comment: This article has been replaced by gr-qc/041201
Transforming aquatic agricultural systems towards gender equality: a five country review
Aquatic agricultural systems (AAS) are systems in which the annual production dynamics of freshwater and/or coastal ecosystems contribute significantly to total household income. Improving the livelihood security and wellbeing of the estimated 250 million poor people dependent on AAS in Bangladesh, Cambodia, the Philippines, the Solomon Islands and Zambia is the goal of the Worldfish Center-led Consortium Research Program (CRP), âHarnessing the development potential of aquatic agricultural systems for development.â One component expected to contribute to sustainably achieving this goal is enhancing the gender and wider social equity of the social, economic and political systems within which the AAS function. The CRPâs focus on social equity, and particularly gender equity, responds to the limited progress to date in enhancing the inclusiveness of development outcomes through interventions that offer improved availability of resources and technologies without addressing the wider social constraints that marginalized populations face in making use of them. The CRP aims to both offer improved availability and address the wider social constraints in order to determine whether a multi-level approach that engages with individuals, households and communities, as well as the wider social, economic and political contexts in which they function, is more successful in extending developmentâs benefits to women and other excluded groups. Designing the research in development initiatives to test this hypothesis requires a solid understanding of each CRP countryâs social, cultural and economic contexts and of the variations across them. This paper provides an initial input into developing this knowledge, based on a review of literature on agriculture, aquaculture and gender relations within the five focal countries. Before delving into the findings of the literature review, the paper first justifies the expectation that successfully achieving lasting wellbeing improvements for poor women and men dependent on AAS rests in part on advances in gender equity, and in light of this justification, presents the AAS CRPâs conceptual frame
Abundance Analysis of the Extremely Fast ONeMg Novae V838 Herculis and V4160 Sagittarii
V838 Her and V4160 Sgr were two of the fastest classical novae ever observed, exhibiting light curve declines of 2 mag in less than 2 days. Both novae also showed strong neon emission lines, indicative of an outburst occurring on an oxygen-neon-magnesium white dwarf. Being the brighter of the two, V838 Her has an extensive set of X-ray to radio observations obtained during its first year after outburst. V4160 Sgr has a more modest set of ultraviolet and optical spectra, which show it to be similar to V838 Her, not just in its light curve evolution but also in its spectral development. The observed attributes imply that these novae occurred on extremely massive white dwarfs. This paper uses the Cloudy photoionization code to fit multiple epochs of emission line spectra to determine the elemental abundances of the ejecta of V838 Her and V4160 Sgr
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