13,479 research outputs found
Time-Reversal Violating Schiff Moment of 225Ra
We use the Skyrme-Hartree-Fock method, allowing all symmetries to be broken,
to calculate the time-reversal-violating nuclear Schiff moment (which induces
atomic electric dipole moments) in the octupole-deformed nucleus 225Ra. Our
calculation includes several effects neglected in earlier work, including self
consistency and polarization of the core by the last nucleon. We confirm that
the Schiff moment is large compared to those of reflection-symmetric nuclei,
though ours is generally a few times smaller than recent estimates.Comment: Typos corrected, references added, minor changesin text. Version to
appear in PRC. 10 pages, 4 figure
Reducing the fine-tuning of gauge-mediated SUSY breaking
Despite their appealing features, models with gauge-mediated supersymmetry
breaking (GMSB) typically present a high degree of fine-tuning, due to the
initial absence of the top trilinear scalar couplings, . In this paper,
we carefully evaluate such a tuning, showing that is worse than per mil in the
minimal model. Then, we examine some existing proposals to generate
term in this context. We find that, although the stops can be made lighter,
usually the tuning does not improve (it may be even worse), with some
exceptions, which involve the generation of at one loop or tree level. We
examine both possibilities and propose a conceptually simplified version of the
latter; which is arguably the optimum GMSB setup (with minimal matter content),
concerning the fine-tuning issue. The resulting fine-tuning is better than one
per mil, still severe but similar to other minimal supersymmetric standard
model constructions. We also explore the so-called "little
problem", i.e. the fact that a large -term is normally accompanied by a
similar or larger sfermion mass, which typically implies an increase in the
fine-tuning. Finally, we find the version of GMSB for which this ratio is
optimized, which, nevertheless, does not minimize the fine-tuning.Comment: 16 pages, 11 figures, 1 appendix. Discussion extended, matches EPJC
published versio
Identification of redundant and synergetic circuits in triplets of electrophysiological data
Neural systems are comprised of interacting units, and relevant information
regarding their function or malfunction can be inferred by analyzing the
statistical dependencies between the activity of each unit. Whilst correlations
and mutual information are commonly used to characterize these dependencies,
our objective here is to extend interactions to triplets of variables to better
detect and characterize dynamic information transfer. Our approach relies on
the measure of interaction information (II). The sign of II provides
information as to the extent to which the interaction of variables in triplets
is redundant (R) or synergetic (S). Here, based on this approach, we calculated
the R and S status for triplets of electrophysiological data recorded from
drug-resistant patients with mesial temporal lobe epilepsy in order to study
the spatial organization and dynamics of R and S close to the epileptogenic
zone (the area responsible for seizure propagation). In terms of spatial
organization, our results show that R matched the epileptogenic zone while S
was distributed more in the surrounding area. In relation to dynamics, R made
the largest contribution to high frequency bands (14-100Hz), whilst S was
expressed more strongly at lower frequencies (1-7Hz). Thus, applying
interaction information to such clinical data reveals new aspects of
epileptogenic structure in terms of the nature (redundancy vs. synergy) and
dynamics (fast vs. slow rhythms) of the interactions. We expect this
methodology, robust and simple, can reveal new aspects beyond pair-interactions
in networks of interacting units in other setups with multi-recording data sets
(and thus, not necessarily in epilepsy, the pathology we have approached here).Comment: 31 pages, 6 figures, 3 supplementary figures. To appear in the
Journal of Neural Engineering in its current for
Is the transition redshift a new cosmological number?
Observations from Supernovae Type Ia (SNe Ia) provided strong evidence for an
expanding accelerating Universe at intermediate redshifts. This means that the
Universe underwent a transition from deceleration to acceleration phases at a
transition redshift of the order unity whose value in principle depends
on the cosmology as well as on the assumed gravitational theory. Since
cosmological accelerating models endowed with a transition redshift are
extremely degenerated, in principle, it is interesting to know whether the
value of itself can be observationally used as a new cosmic
discriminator. After a brief discussion of the potential dynamic role played by
the transition redshift, it is argued that future observations combining SNe
Ia, the line-of-sight (or "radial") baryon acoustic oscillations, the
differential age of galaxies, as well as the redshift drift of the spectral
lines may tightly constrain , thereby helping to narrow the parameter
space for the most realistic models describing the accelerating Universe.Comment: 12 pages, 5 figures. Some discussions about how to estimate the
transition redshift have been added. New data by Planck and H(z) data have
been mentioned. New references have been adde
Vibrations on pulse tube based Dry Dilution Refrigerators for low noise measurements
Dry Dilution Refrigerators (DDR) based on pulse tube cryo-coolers have
started to replace Wet Dilution Refrigerators (WDR) due to the ease and low
cost of operation. However these advantages come at the cost of increased
vibrations, induced by the pulse tube. In this work, we present the vibration
measurements performed on three different commercial DDRs. We describe in
detail the vibration measurement system we assembled, based on commercial
accelerometers, conditioner and DAQ, and examined the effects of the various
damping solutions utilized on three different DDRs, both in the low and high
frequency regions. Finally, we ran low temperature, pseudo-massive (30 and 250
g) germanium bolometers in the best vibration-performing system under study and
report on the results
What is a Natural SUSY scenario?
The idea of "Natural SUSY", understood as a supersymmetric scenario where the
fine-tuning is as mild as possible, is a reasonable guide to explore
supersymmetric phenomenology. In this paper, we re-examine this issue in the
context of the MSSM including several improvements, such as the mixing of the
fine-tuning conditions for different soft terms and the presence of potential
extra fine-tunings that must be combined with the electroweak one. We give
tables and plots that allow to easily evaluate the fine-tuning and the
corresponding naturalness bounds for any theoretical model defined at any
high-energy (HE) scale. Then, we analyze in detail the complete fine-tuning
bounds for the unconstrained MSSM, defined at any HE scale. We show that
Natural SUSY does not demand light stops. Actually, an average stop mass below
800 GeV is disfavored, though one of the stops might be very light. Regarding
phenomenology, the most stringent upper bound from naturalness is the one on
the gluino mass, which typically sets the present level of fine-tuning at
. However, this result presents a strong dependence on the HE
scale. E.g. if the latter is GeV the level of fine-tuning is four
times less severe. Finally, the most robust result of Natural SUSY is by far
that Higgsinos should be rather light, certainly below 700 GeV for a
fine-tuning of or milder. Incidentally, this upper bound is not
far from TeV, which is the value required if dark matter is made of
Higgsinos.Comment: 41 pages, 8 figures, 9 tables. References added, matches JHEP
published versio
Relevance of accounting information to public sector accountability: a study of Brazilian federal public universities
Public Sector Accounting is particularly relevant in the context of New Public Management because it is the most important approach for recording and reporting management acts, helping public managers to achieve their objectives regarding internal and external reporting for accountability purposes.
This study main objective is to evaluate the usefulness of accounting information as well as the findings of non-compliance in the opinions of audits conducted by Internal Control System in explaining the quality of 51 Brazilian Federal Universities, using data from the General Index of Courses published in 2007.
The findings demonstrate that accounting information of the Brazilian Federal Universities, particularly current expenses and operating assets are significant to explain the quality index reached by the HEIs, endorsing the relevance of accounting to accountability, considering the diverse stakeholders. The evidence also reveals that qualifications in audit opinions are not relevant to explain the universities performance.
The findings may assist as criteria for formulating public policies on resource allocation in education, and also contribute to improve auditing systems in the Internal and External Control of the Education Sector.info:eu-repo/semantics/acceptedVersio
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