2,636 research outputs found
Lepton Number Violation in Supersymmetric Grand Unified Theories
We argue that the nature of the global conservation laws in Supersymmetric
Grand Unified Theories is determined by the basic vacuum configuration in the
model rather than its Lagrangian. It is shown that the suppression of baryon
number violation in a general (R-parity violating) superpotential can naturally
appear in some extended SU(N) SUSY GUTs which, among other degenerate
symmetry-breaking vacua, have a missing VEV vacuum configuration giving a
solution to the doublet-triplet splitting problem. We construct SU(7) and SU(8)
GUTs where the effective lepton number violating couplings immediately evolve,
while the baryon number non-conserving ones are safely projected out as the GUT
symmetry breaks down to that of the MSSM. However at the next stage, when SUSY
breaks, the radiative corrections shift the missing VEV components to some
nonzero values of order M_{SUSY}, thereby inducing the ordinary Higgs doublet
mass, on the one hand, and tiny baryon number violation, on the other. So, a
missing VEV solution to the gauge hierarchy problem leads at the same time to a
similar hierarchy of baryon vs lepton number violation.Comment: 15 page LaTeX fil
Massless radiation from Strings: quantum spectrum average statistics and cusp-kink configurations
We derive general formulae for computing the average spectrum for Bosonic or
Fermionic massless emission from generic or particular sets of closed
superstring quantum states, among the many occurring at a given large value of
the number operator. In particular we look for states that can produce a
Bosonic spectrum resembling the classical spectrum expected for peculiar
cusp-like or kink-like classical configurations, and we perform a statistical
counting of their average number. The results can be relevant in the framework
of possible observations of the radiation emitted by cosmic strings.Comment: 13 pages, 4 figures, improved explanations, an appendix added on
rotating folded strin
Data acquisition electronics and reconstruction software for directional detection of Dark Matter with MIMAC
Directional detection of galactic Dark Matter requires 3D reconstruction of
low energy nuclear recoils tracks. A dedicated acquisition electronics with
auto triggering feature and a real time track reconstruction software have been
developed within the framework of the MIMAC project of detector. This
auto-triggered acquisition electronic uses embedded processing to reduce data
transfer to its useful part only, i.e. decoded coordinates of hit tracks and
corresponding energy measurements. An acquisition software with on-line
monitoring and 3D track reconstruction is also presented.Comment: 17 pages, 12 figure
Associations between sole ulcer, white line disease and digital dermatitis and the milk yield of 1824 dairy cows on 30 dairy cow farms in England and Wales from February 2003âNovember 2004
The milk yields of 1824 cows were used to investigate the effect of lesion-specific causes of lameness, based on farmer treatment and diagnosis of lame cows, on milk yield. A three level hierarchical model of repeated test day yields within cows within herds was used to investigate the impact of lesion-specific causes of lameness (sole ulcer, white line disease, digital dermatitis and other causes) on milk yield before and after treatment compared with unaffected cows. Cattle which developed sole ulcer (SU) and white line disease (WLD) were higher yielding cattle before they were diagnosed. Their milk production fell to below that of the mean of unaffected cows before diagnosis and remained low after diagnosis. In cattle which developed digital dermatitis (DD) there was no significant difference in milk yield before treatment and a slightly raised milk yield immediately after treatment. The estimated milk loss attributable to SU and WLD was approximately 570kg and 370kg respectively. These results highlight that specific types of lameness vary by herds and within herds they are associated with higher yielding cattle. Consequently lesion-specific lameness reduction programmes targeting the cow and farm specific causes of lameness might be more effective than generic recommendations. They also highlight the importance of milk loss when estimating the economic impact of SU and WLD on the farms profitability
Variability monitoring of the hydroxyl maser emission in G12.889+0.489
Through a series of observations with the Australia Telescope Compact Array we have monitored the variability of ground-state hydroxyl maser emission from
G12.889+0.489 in all four Stokes polarisation products. These observations were motivated by the known periodicity in the associated 6.7-GHz methanol maser emission. A total of 27 epochs of observations were made over 16 months. No emission was seen from either the 1612 or 1720 MHz satellite line transitions (to a typical five sigma upper limit of 0.2 Jy). The peak flux densities of the 1665 and 1667 MHz emission were observed to vary at a level of âŒ20% (with the exception of one epoch which dropped by 640%). There was no distinct flaring activity at any epoch, but there was a weak indication of periodic variability, with a period and phase of minimum emission similar to that of methanol. There is no significant variation in the polarised properties of the hydroxyl, with Stokes Q and U flux densities varying in accord with the Stokes I intensity (linear polarisation, P, varying by 620%) and the right and left circularly polarised components varying by 633% at 1665-MHz and 638% at 1667-MHz. These observations are the first monitoring observations of the hydroxyl maser emission from G12.889+0.489
Emission Spectrum of Fundamental Strings: An Algebraic Approach
We formulate a linear difference equation which yields averaged
semi-inclusive decay rates for arbitrary, not necessarily large, values of the
masses. We show that the rates for decays M \to m+\M' of typical heavy open
strings are independent of the masses and , and compute the ``mass
deffect''. For closed strings we find decay rates proportional to , where is the reduced mass of the decy products. Our
method yields exact interaction rates valid for all mass ranges and may provide
a fully microscopic basis, not limited to the long string approximation, for
the interactions in the Boltzmann equation approach to hot string gases.Comment: 35 pages, 3 figure
Palatini Variational Principle for an Extended Einstein-Hilbert Action
We consider a Palatini variation on a generalized Einstein-Hilbert action. We
find that the Hilbert constraint, that the connection equals the Christoffel
symbol, arises only as a special case of this general action, while for
particular values of the coefficients of this generalized action, the
connection is completely unconstrained. We discuss the relationship between
this situation and that usually encountered in the Palatini formulation.Comment: 14 pages, LaTe
Motivational and control mechanisms underlying adolescent versus adult alcohol use
Increased motivation towards alcohol use and suboptimal behavioral control are suggested
to predispose adolescents to alcohol use disorders (AUDs). Paradoxically however, most adolescent
AUDs resolve over time without any formal intervention, suggesting adolescent resilience to AUDs.
Importantly, studies directly comparing adolescent and adult alcohol use are largely missing.
We therefore aimed to unravel the moderating role of age in the relation between alcohol use and
motivational and control-related cognitive processes in 45 adolescent drinkers compared to 45 adults.
We found that enhancement drinking motives and impulsivity related positively to alcohol use.
Although enhancement drinking motives and impulsivity were higher in adolescents, the strength of
the relation between these measures and alcohol use did not differ between age groups. None of
the alcohol use-related motivational measures (i.e., craving, attentional bias, and approach bias) and
behavioral control measures (i.e., interference control, risky decision making, and working-memory)
were associated with alcohol use or differed between age groups. These findings support the role of
impulsivity and affective sensitivity in adolescent drinking but question the moderating role of age
therein. The current study contributes towards understanding the role of age in the relation between
alcohol use and cognition
Dependence of direct detection signals on the WIMP velocity distribution
The signals expected in WIMP direct detection experiments depend on the
ultra-local dark matter distribution. Observations probe the local density,
circular speed and escape speed, while simulations find velocity distributions
that deviate significantly from the standard Maxwellian distribution. We
calculate the energy, time and direction dependence of the event rate for a
range of velocity distributions motivated by recent observations and
simulations, and also investigate the uncertainty in the determination of WIMP
parameters. The dominant uncertainties are the systematic error in the local
circular speed and whether or not the MW has a high density dark disc. In both
cases there are substantial changes in the mean differential event rate and the
annual modulation signal, and hence exclusion limits and determinations of the
WIMP mass. The uncertainty in the shape of the halo velocity distribution is
less important, however it leads to a 5% systematic error in the WIMP mass. The
detailed direction dependence of the event rate is sensitive to the velocity
distribution. However the numbers of events required to detect anisotropy and
confirm the median recoil direction do not change substantially.Comment: 21 pages, 7 figures, v2 version to appear in JCAP, minor change
Large N limit of Extremal Non-supersymmetric Black Holes
The large N limit of extremal non-supersymmetric Type-I five-dimensional
string black holes is studied from the point of view of D-branes.
We find that the agreement between the D-brane and the black-hole picture is
due to an asymptotic restoration of supersymmetry in the large limit in
which both pictures are compared.
In that limit Type-I string perturbation theory is effectively embedded into
a Type-IIB perturbation theory with unbroken supersymmetric charges whose
presence guarantees the non-renormalization of mass and entropy as the
effective couplings are increased. In this vein, we also study the near-horizon
geometry of the Type-I black hole using D5-brane probes to find that the low
energy effective action for the probe is identical to the corresponding one in
the auxiliary Type-IIB theory in the large N limit.Comment: 25 pages, harvmac, typos corrected and references adde
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