26,158 research outputs found
New Q-ball Solutions in Gauge-Mediation, Affleck-Dine Baryogenesis and Gravitino Dark Matter
Affleck-Dine (AD) baryogenesis along a d=6 flat direction in gauge-mediated
supersymmetry-breaking (GMSB) models can produce unstable Q-balls which
naturally have field strength similar to the messenger scale. In this case a
new kind of Q-ball is formed, intermediate between gravity-mediated and
gauge-mediated type. We study in detail these new Q-ball solutions, showing how
their properties interpolate between standard gravity-mediated and
gauge-mediated Q-balls as the AD field becomes larger than the messenger scale.
It is shown that E/Q for the Q-balls can be greater than the nucleon mass but
less than the MSSM-LSP mass, leading to Q-ball decay directly to Standard Model
fermions with no MSSM-LSP production. More significantly, if E/Q is greater
than the MSSM-LSP mass, decaying Q-balls can provide a natural source of
non-thermal MSSM-LSPs, which can subsequently decay to gravitino dark matter
without violating nucleosynthesis constraints. The model therefore provides a
minimal scenario for baryogenesis and gravitino dark matter in the
gauge-mediated MSSM, requiring no new fields.Comment: 13 pages, 9 figures. Some corrections and additional discussion.
Version published in JCA
Deterministic dense coding and entanglement entropy
We present an analytical study of the standard two-party deterministic
dense-coding protocol, under which communication of perfectly distinguishable
messages takes place via a qudit from a pair of non-maximally entangled qudits
in pure state |S>. Our results include the following: (i) We prove that it is
possible for a state |S> with lower entanglement entropy to support the sending
of a greater number of perfectly distinguishable messages than one with higher
entanglement entropy, confirming a result suggested via numerical analysis in
Mozes et al. [Phys. Rev. A 71 012311 (2005)]. (ii) By explicit construction of
families of local unitary operators, we verify, for dimensions d = 3 and d=4, a
conjecture of Mozes et al. about the minimum entanglement entropy that supports
the sending of d + j messages, j = 2, ..., d-1; moreover, we show that the j=2
and j= d-1 cases of the conjecture are valid in all dimensions. (iii) Given
that |S> allows the sending of K messages and has the square roof of c as its
largest Schmidt coefficient, we show that the inequality c <= d/K, established
by Wu et al. [ Phys. Rev. A 73, 042311 (2006)], must actually take the form c <
d/K if K = d+1, while our constructions of local unitaries show that equality
can be realized if K = d+2 or K = 2d-1.Comment: 19 pages, 2 figures. Published versio
A very deep Chandra observation of Abell 1795: The Cold Front and Cooling Wake
We present a new analysis of very deep Chandra observations of the galaxy
cluster Abell 1795. Utilizing nearly 750 ks of net ACIS imaging, we are able to
resolve the thermodynamic structure of the Intracluster Medium (ICM) on length
scales of ~ 1 kpc near the cool core. We find several previously unresolved
structures, including a high pressure feature to the north of the BCG that
appears to arise from the bulk motion of Abell 1795's cool core. To the south
of the cool core, we find low temperature (~ 3 keV), diffuse ICM gas extending
for distances of ~ 50 kpc spatially coincident with previously identified
filaments of H-alpha emission. Gas at similar temperatures is also detected in
adjacent regions without any H-alpha emission. The X-ray gas coincident with
the H-alpha filament has been measured to be cooling spectroscopically at a
rate of ~ 1 Solar Masses/ yr, consistent with measurements of the star
formation rate in this region as inferred from UV observations, suggesting that
the star formation in this filament as inferred by its H and UV
emission can trace its origin to the rapid cooling of dense, X-ray emitting
gas. The H-alpha filament is not a unique site of cooler ICM, however, as ICM
at similar temperatures and even higher metallicities not cospatial with
H emission is observed just to the west of the H-alpha filament,
suggesting that it may have been uplifted by Abell 1795's central active
galaxy. Further simulations of cool core sloshing and AGN feedback operating in
concert with one another will be necessary to understand how such a dynamic
cool core region may have originated and why the H-alpha emission is so
localized with respect to the cool X-ray gas despite the evidence for a
catastrophic cooling flow.Comment: 14 Pages, 10 Figures, Resubmitted to ApJ after first referee report,
Higher Resolution Figures available upon reques
The Influence of Formulation, Buffering, pH and Divalent Cations on the Activity of Endothall on Hydrilla.
Endothall has been used as an aquatic herbicide for more
than 40 years and provides very effective weed control of
many weeds. Early research regarding the mechanism-of-action
of endothall contradicts the symptomology normally associated
with the product. Recent studies suggest endothall
is a respiratory toxin but the mechanism-of-action remains
unknown. To further elucidate the activity of endothall, several
endothall formulations were evaluated for their effects
on ion leakage, oxygen consumption and photosynthetic oxygen
evolution from hydrilla shoot tips. The influence of pH,
buffering and divalent cations was also evaluated. (PDF contains 6 pages.
Exoplanetary atmosphere target selection in the era of comparative planetology
The large number of new planets expected from wide-area transit surveys means
that follow-up transmission spectroscopy studies of their atmospheres will be
limited by the availability of telescope assets. We argue that telescopes
covering a broad range of apertures will be required, with even 1m-class
instruments providing a potentially important contribution. Survey strategies
that employ automated target selection will enable robust population studies.
As part of such a strategy, we propose a decision metric to pair the best
target to the most suitable telescope, and demonstrate its effectiveness even
when only primary transit observables are available. Transmission spectroscopy
target selection need not therefore be impeded by the bottle-neck of requiring
prior follow-up observations to determine the planet mass. The decision metric
can be easily deployed within a distributed heterogeneous network of telescopes
equipped to undertake either broadband photometry or spectroscopy. We show how
the metric can be used either to optimise the observing strategy for a given
telescope (e.g. choice of filter) or to enable the selection of the best
telescope to optimise the overall sample size. Our decision metric can also
provide the basis for a selection function to help evaluate the statistical
completeness of follow-up transmission spectroscopy datasets. Finally, we
validate our metric by comparing its ranked set of targets against lists of
planets that have had their atmospheres successfully probed, and against some
existing prioritised exoplanet lists.Comment: 20 pages, 16 figures, 3 tables. Revision 3, accepted by MNRAS.
Improvements include always using planetary masses where available and
reliable, treatment for sky backgrounds and out-of-transit noise and a use
case for defocused photometr
Paradox in Wave-Particle Duality
We report on the simultaneous determination of complementary wave and particle aspects of light in a double-slit type "welcher-weg" experiment beyond the limitations set by Bohr's Principle of Complementarity. Applying classical logic, we verify the presence of sharp interference in the single photon regime, while reliably maintaining the information about the particular pinhole through which each individual photon had passed. This experiment poses interesting questions on the validity of Complementarity in cases where measurements techniques that avoid Heisenberg's uncertainty principle and quantum entanglement are employed. We further argue that the application of classical concepts of waves and particles as embodied in Complementarity leads to a logical inconsistency in the interpretation of this experiment
Helmholtz solitons in optical materials with a dual power-law refractive index
A nonlinear Helmholtz equation is proposed for modelling scalar optical beams in uniform planar waveguides whose refractive index exhibits a purely-focusing dual powerlaw
dependence on the electric field amplitude. Two families of exact analytical solitons, describing forward- and backward-propagating beams, are derived. These solutions are
physically and mathematically distinct from those recently discovered for related nonlinearities. The geometry of the new solitons is examined, conservation laws are reported,
and classic paraxial predictions are recovered in a simultaneous multiple limit. Conventional semi-analytical techniques assist in studying the stability of these nonparaxial solitons, whose propagation properties are investigated through extensive simulations
Recommended from our members
UK Research Information Shared Service (UKRISS) Final Report, July 2014
The reporting of research information is a complex and expensive activity for research organisations (ROs). There is little alignment between funders of the reporting requests made to institutions and requests made to individual researchers about their research outputs and outcomes. This inevitably results in duplication and increased costs across the sector, whilst limiting the potential sharing and reuse of the information. The UK Research Information Shared Service (UKRISS) project conducted a feasibility and scoping study for the reporting of research information at a national level based on CERIF (Common European Research Information Format), with the objective of increasing efficiency, productivity and quality across the sector. The aim was to define and prototype solutions which are compelling, easy to use, have a low entry barrier, and support innovative information sharing and benchmarking. CERIF has emerged as the preferred format for expressing research information across Europe. To date, CERIF has been piloted for specific applications, but not as a format for reporting requirements across all UK ROs. The final report presents the work carried out by the UKRISS project, including requirements gathering, modelling and prototyping, as well as recommendation for sustainability. UKRISS was divided into two phases. Phase 1, mapping the reporting landscape, ran from March 2012 to December 2012. Phase 2, exploring delivery of potential solutions, began in February 2013 and ended in December 2013
A Systematic Review of Ecological and Production Outcomes under Rest-Grazing Systems
With increasing pressure on grazing lands throughout the world, there is a growing need to balance sustainable management of livestock to meet food production and environmental impacts. Grazing management practices that incorporate periods of planned rest between grazing events (RG) may achieve both ecological and production goals simultaneously. We conducted a systematic review of global literature that compared ecological and production outcomes of RG systems with either continuously grazed (CG) or ungrazed (UG) areas. In addition, we evaluated the extent to which ecological and livestock production outcomes have been assessed simultaneously in these studies and identified future research needs. A large proportion of the literature reported no difference (neutral response) between the different management systems. However, where differences did occur, the response of biodiversity, land condition and livestock production metrics was more often positive under RG than CG. When RG was compared to UG areas, differences were predominantly positive for plant biodiversity metrics, but negative for invertebrate biodiversity, ground cover and plant biomass. Only a small proportion of studies considered the effect of RG on both ecological and production outcomes simultaneously. An understanding of both ecological and production trade-offs associated with different grazing management strategies is essential to make informed decisions about best-management practices for joint production and ecological outcomes across the world’s grazing lands
- …