631 research outputs found
Large-scale anomalies from primordial dissipation
We analyze an inflationary model in which part of the power in density
perturbations arises due to particle production. The amount of particle
production is modulated by an auxiliary field. Given an initial gradient for
the auxiliary field, this model produces a hemispherical power asymmetry and a
suppression of power at low multipoles similar to those observed by WMAP and
Planck in the CMB temperature. It also predicts an additive contribution to
with support only at very small that is aligned with the
direction of the power asymmetry and has a definite sign, as well as small
oscillations in the power spectrum at all .Comment: 1+15 pages, 7 figure
D-brane scattering and annihilation
We study the dynamics of parallel brane-brane and brane-antibrane scattering
in string theory in flat spacetime, focusing on the pair production of open
strings that stretch between the branes. We are particularly interested in the
case of scattering at small impact parameter , where there is a
tachyon in the spectrum when a brane and an antibrane approach within a string
length. Our conclusion is that despite the tachyon, branes and antibranes can
pass through each other with only a very small probability of annihilating, so
long as is small and the relative velocity is neither too small nor
too close to 1. Our analysis is relevant also to the case of charged open
string production in world-volume electric fields, and we make use of this
T-dual scenario in our analysis. We briefly discuss the application of our
results to a stringy model of inflation involving moving branes.Comment: 25+7 pages, 5 figure
Inflation from Flux Cascades
When electric-type flux threads compact extra dimensions, a quantum
nucleation event can break a flux line and initiate a cascade that unwinds many
units of flux. Here, we present a novel mechanism for inflation based on this
phenomenon. From the 4D point of view, the cascade begins with the formation of
a bubble containing an open Friedmann-Robertson-Walker cosmology, but the
vacuum energy inside the bubble is initially only slightly reduced, and
subsequently decreases gradually throughout the cascade. If the initial flux
number Q_0 ~ O(100), during the cascade the universe can undergo N ~ 60 efolds
of inflationary expansion with gradually decreasing Hubble constant, producing
a nearly scale-invariant spectrum of adiabatic density perturbations with
amplitude and tilt consistent with observation, and a potentially observable
level of non-Gaussianity and tensor modes. The power spectrum has a small
oscillatory component that does not decay away during inflation, with a period
set approximately by the light-crossing time of the compact dimension(s). Since
the ingredients are fluxes threading compact dimensions, this mechanism fits
naturally into the string landscape, but does not appear to suffer from the eta
problem or require fine-tuning (beyond the usual anthropic requirement of small
vacuum energy after reheating).Comment: 5 pages, 1 figur
Unwinding Inflation
Higher-form flux that extends in all 3+1 dimensions of spacetime is a source
of positive vacuum energy that can drive meta-stable eternal inflation. If the
flux also threads compact extra dimensions, the spontaneous nucleation of a
bubble of brane charged under the flux can trigger a classical cascade that
steadily unwinds many units of flux, gradually decreasing the vacuum energy
while inflating the bubble, until the cascade ends in the self-annihilation of
the brane into radiation. With an initial number of flux quanta Q_{0} \simgeq
N, this can result in N efolds of inflationary expansion while producing a
scale-invariant spectrum of adiabatic density perturbations with amplitude and
tilt consistent with observation. The power spectrum has an oscillatory
component that does not decay away during inflation, relatively large tensor
power, and interesting non-Gaussianities. Unwinding inflation fits naturally
into the string landscape, and our preliminary conclusion is that consistency
with observation can be attained without fine-tuning the string parameters. The
initial conditions necessary for the unwinding phase are produced automatically
by bubble formation, so long as the critical radius of the bubble is smaller
than at least one of the compact dimensions threaded by flux.Comment: 29+15 pages, 10 figures, published versio
Why Companies Do Not Renew Their EMAS Registration? An Exploratory Research
The Eco-Management and Audit Scheme (EMAS) is the official Environmental Management System (EMS) issued by the European Union (EU). Italy is the country where EMAS is most widespread, accounting for over 1000 registered organizations. Since entry into the force of the Regulation in 1997, the number of registrations has constantly grown until 2008, when the figures started to drop. The phenomena are due to both the decrease of the annual registration rate and the lack of renewals. According to the Italian Institute for Environmental Protection and Research (ISPRA), in recent years, an increasing number of organizations decided to withdraw from EMAS registration. The purpose of this paper is to analyze the reasons of this negative trend. The first step consisted of a literature review concerning the main barriers, difficulties, and costs incurred by EMAS-registered organizations. Subsequently, this information was integrated with data about the evolution of EMAS registrations and the results of a previous survey, which involved the entire population of registered firms. The present exploratory research highlighted economic and operational domains concerning the cancellation trends that deserve a deeper investigation, which will be conducted through a questionnaire addressed to Italian firms that did not renew the registration in the last lustrum. The intended output will allow us to identify stakeholders' priority intervention areas in order to suggest an operative strategy to reduce EMAS cancellation rates, addressed to Member States (MS) Competent Bodies
Extra virgin olive oil and cardiovascular diseases: benefits for human health
The cardioprotective properties of Mediterranean Diet were demonstrated for the first time from the Seven Country Study. In the last few decades, numerous epidemiological studies, as well as intervention trial, confirmed this observation, pointing out the close relationship between the Mediterranean diet and cardiovascular diseases. In this context, extra virgin olive oil (EVOO), the most representative component of this diet, seems to be relevant in lowering the incidence of cardiovascular events, including myocardial infarction and stroke. From a chemical point of view, 98-99% of the total weight of EVOO is represented by fatty acids, especially monounsaturated fatty acids such as oleic acid. Tocopherols, polyphenols and other minor constituents represent the remaining 1-2%. All these components may potentially contribute to "health maintenance" with their beneficial effects by EVOOO
Recombinant factor VIIa concentrate versus plasma-derived concentrates for treating acute bleeding episodes in people with haemophilia and inhibitors
In people with haemophilia, therapeutic clotting agents might be recognised as a foreign protein and induce anti-factor VIII antibodies, known as 'inhibitors'. Drugs insensitive to such antibodies, either recombinant or plasma-derived, are called factor VIII 'by-passing' agents and used for treatment of bleeding in people with inhibitors
Experimental Correlation-Boosted Quantum Engine
We design and experimentally implement a two-qubit quantum correlated SWAP
heat engine that allows to achieve an efficiency above the standard Carnot
limit, and to boost the amount of extractable work, in a wider qubit energy-gap
ratio window, with respect to engine's cycle in the absence of initial qubit
correlations. The boosted efficiency arises from a trade-off between the
entropy production and the consumption of quantum correlations during the full
thermodynamic cycle. We derive a generalized second-law limit and
experimentally demonstrate the engine efficiency enhancement by tailoring the
qubits effective energy gap and temperature, using an IBM quantum processor
Immunomodulators and immunosuppressants for relapsing-remitting multiple sclerosis: a network meta-analysis
Different therapeutic strategies are available for the treatment of people with relapsing-remitting multiple sclerosis (RRMS), including immunomodulators, immunosuppressants and biologics. Although there is consensus that these therapies reduce the frequency of relapses, their relative benefit in delaying new relapses or disability worsening remains unclear due to the limited number of direct comparison trials
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