30,839 research outputs found
Proton Decay, Fermion Masses and Texture from Extra Dimensions in SUSY GUTs
In supersymmetry, there are gauge invariant dimension 5 proton decay
operators which must be suppressed by a mass scale much larger than the Planck
mass. It is natural to expect that this suppression should be explained by a
mechanism that explains the hierarchical structure of the fermion mass
matrices. We apply this argument to the case where wave functions of chiral
multiplets are localized under a kink background along an extra spatial
dimension and the Yukawa couplings as well as the coefficients of the proton
decay operators are determined by the overlap of the relevant wave functions. A
configuration is found in the context of SU(5) supersymmetric grand unified
theory that yields realistic values of quark masses, mixing angles, CP phase
and charged lepton masses and sufficiently small genuine dimension 5 proton
decay operators. Inclusion of SU(5) breaking effects is essential in order to
obtain non-vanishing CP phase as well as correct lepton masses. The resulting
mass matrix has a texture structure in which texture zeros are a consequence of
extremely small overlap of the wave functions. Our approach requires explicit
breaking of supersymmetry in the extra dimension, which can be realized in
(de)constructing extra dimension.Comment: 23 pages, 2 figures, comments adde
On Extended Electroweak Symmetries
We discuss extensions of the Standard Model through extending the electroweak
gauge symmetry. An extended electroweak symmetry requires a list of extra
fermionic and scalar states. The former is necessary to maintain cancellation
of gauge anomalies, and largely fixed by the symmetry embedding itself. The
latter is usually considered quite arbitrary, so long as a vacuum structure
admitting the symmetry breaking is allowed. Anomaly cancellation may be used to
link the three families of quarks and leptons together, given a perspective on
flavor physics. It is illustrated lately that the kind of models may also have
the so-called little Higgs mechanism incorporated. This more or less fixes the
scalar sector and take care of the hierarchy problem, making such models of
extended electroweak symmetries quite appealing candidates as TeV scale
effective field theories.Comment: 1+8 pages of latex with ws-procs9x6.cls; talk presented at Coral
Gables Conference 200
Fermi Edge Resonances in Non-equilibrium States of Fermi Gases
We formulate the problem of the Fermi Edge Singularity in non-equilibrium
states of a Fermi gas as a matrix Riemann-Hilbert problem with an integrable
kernel. This formulation is the most suitable for studying the singular
behavior at each edge of non-equilibrium Fermi states by means of the method of
steepest descent, and also reveals the integrable structure of the problem. We
supplement this result by extending the familiar approach to the problem of the
Fermi Edge Singularity via the bosonic representation of the electronic
operators to non-equilibrium settings. It provides a compact way to extract the
leading asymptotes.Comment: Accepted for publication, J. Phys.
Progress in Electroweak Baryogenesis
Recent work on generating the excess of matter over antimatter in the early
universe during the electroweak phase transition is reviewed.Comment: 50 pages (figures on request), uses harvmac (table of contents
correct for "l" format), UCSD-93-2,BU-HEP-93-
Gauge/Anomaly Syzygy and Generalized Brane World Models of Supersymmetry Breaking
In theories in which SUSY is broken on a brane separated from the MSSM matter
fields, supersymmetry breaking is naturally mediated in a variety of ways.
Absent other light fields in the theory, gravity will mediate supersymmetry
breaking through the conformal anomaly. If gauge fields propagate in the extra
dimension they, too, can mediate supersymmetry breaking effects. The presence
of gauge fields in the bulk motivates us to consider the effects of new
messenger fields with holomorphic and non-holomorphic couplings to the
supersymmetry breaking sector. These can lead to contributions to the soft
masses of MSSM fields which dramatically alter the features of brane world
scenarios of supersymmetry breaking. In particular, they can solve the negative
slepton mass squared problem of anomaly mediation and change the predictions of
gaugino mediation.Comment: 4 pages, RevTe
The Delta-Delta Intermediate State in 1S0 Nucleon-Nucleon Scattering From Effective Field Theory
We examine the role of the Delta-Delta intermediate state in low energy NN
scattering using effective field theory. Theories both with and without pions
are discussed. They are regulated with dimensional regularization and MSbar
subtraction. We find that the leading effects of the Delta-Delta state can be
absorbed by a redefinition of the contact terms in a theory with nucleons only.
It does not remove the requirement of a higher dimension operator to reproduce
data out to moderate momentum. The explicit decoupling of the Delta-Delta state
is shown for the theory without pions.Comment: 16 pages, 3 figures, uses harvma
Valuing Options in California Water Markets: A Laboratory Investigation
Risk and reliability dominate water supply discussions in the arid western United States. In the past, water managers built additional storage to mitigate supply risk. The optimal, least expensive storage sites have now been taken, and there are strong, environmental objections to new facilities. Reliability of existing supplies is further diminished due to concerns about endangered species and global climate change. Thus water agencies increasingly turn to contractual mechanisms such as dry-year options to manage supply risk in advance of need. However, although a few water agencies across the West have implemented dry-year options, sufficient data for conventional econometric analysis do not yet exist. We thus utilize experimental economics to analyze the effect of annual dry-year options on water markets. How do market structure (competitive versus market power) and option contract availability affect water price and allocation within a market? Experiment participants trade stochastic realizations of water in a non-uniform double auction parameterized to resemble the California water market. We find that realized gains from trade are on average higher when options can be traded, by 11% in competitive markets and by 21% in dominant buyer markets. Findings in this analysis may assist policymakers in preparing for the next multi-year drought in California.Resource /Energy Economics and Policy,
The Influence of Thermal Pressure on Equilibrium Models of Hypermassive Neutron Star Merger Remnants
The merger of two neutron stars leaves behind a rapidly spinning hypermassive
object whose survival is believed to depend on the maximum mass supported by
the nuclear equation of state, angular momentum redistribution by
(magneto-)rotational instabilities, and spindown by gravitational waves. The
high temperatures (~5-40 MeV) prevailing in the merger remnant may provide
thermal pressure support that could increase its maximum mass and, thus, its
life on a neutrino-cooling timescale. We investigate the role of thermal
pressure support in hypermassive merger remnants by computing sequences of
spherically-symmetric and axisymmetric uniformly and differentially rotating
equilibrium solutions to the general-relativistic stellar structure equations.
Using a set of finite-temperature nuclear equations of state, we find that hot
maximum-mass critically spinning configurations generally do not support larger
baryonic masses than their cold counterparts. However, subcritically spinning
configurations with mean density of less than a few times nuclear saturation
density yield a significantly thermally enhanced mass. Even without decreasing
the maximum mass, cooling and other forms of energy loss can drive the remnant
to an unstable state. We infer secular instability by identifying approximate
energy turning points in equilibrium sequences of constant baryonic mass
parametrized by maximum density. Energy loss carries the remnant along the
direction of decreasing gravitational mass and higher density until instability
triggers collapse. Since configurations with more thermal pressure support are
less compact and thus begin their evolution at a lower maximum density, they
remain stable for longer periods after merger.Comment: 20 pages, 12 figures. Accepted for publication in Ap
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