3,970 research outputs found
Effect of the carbon source in the regulation of flocculation of Ale Brewer yeast strains
Instituto Politécnico do Porto. Fundo de Apoio à Investigação, Programa Plurianual de Unidades de I&D - CIEA/ISEP
Finite Temperature Phase Diagram of Quasi-Two-Dimensional Imbalanced Fermi Gases Beyond Mean-Field
We investigate the superfluid transition temperature of quasi-two-dimensional
imbalanced Fermi gases beyond the mean-field approximation, through the
second-order (or induced) interaction effects. For a balanced Fermi system the
transition temperature is suppressed by a factor . For imbalanced
Fermi systems, the polarization and transition temperature of the tricritical
point are significantly reduced as the two-body binding energy
increases.Comment: 6 pages, 3 figure
Symmetries and Ambiguities in the linear sigma model with light quarks
We investigate the role of undetermined finite contributions generated by
radiative corrections in a linear sigma model with quarks.
Although some of such terms can be absorbed in the renormalization procedure,
one such contribution is left in the expression for the pion decay constant.
This arbitrariness is eliminated by chiral symmetry.Comment: 9 pages. Added references through the text; an author was added due
to an important contribution; corrected typos; the title also was changed.
Submitted to Modern Physics Letter
Disappearing cosmological constant in f(R) gravity
For higher-derivative f(R) gravity where R is the Ricci scalar, a class of
models is proposed which produce viable cosmology different from the LambdaCDM
one at recent times and satisfy cosmological, Solar system and laboratory
tests. These models have both flat and de Sitter space-times as particular
solutions in the absence of matter. Thus, a cosmological constant is zero in
flat space-time, but appears effectively in a curved one for sufficiently large
R. A 'smoking gun' for these models would be small discrepancy in values of the
slope of the primordial perturbation power spectrum determined from galaxy
surveys and CMB fluctuations. On the other hand, a new problem for dark energy
models based on f(R) gravity is pointed which is connected with possible
overproduction of new massive scalar particles (scalarons) arising in this
theory in the very early Universe.Comment: 8 pages, footnote clarified, grammatical typo corrected, references
added, final version to be published in JETP
IFMIF suitability for evaluation of fusion functional materials
The International FusionMaterials Irradiation Facility (IFMIF) is a future neutron source based on the D-Li stripping reaction, planned to test candidate fusionmaterials at relevant fusion irradiation conditions. During the design of IFMIF special attention was paid to the structural materials for the blanket and first wall, because they will be exposed to the most severe irradiation conditions in a fusion reactor. Also the irradiation of candidate materials for solid breeder blankets is planned in the IFMIF reference design.
This paper focuses on the assessment of the suitability of IFMIF irradiation conditions for testing functionalmaterials to be used in liquid blankets and diagnostics systems, since they are been also considered within IFMIF objectives. The study has been based on the analysis and comparison of the main expected irradiation parameters in IFMIF and DEMO reactor
Casimir-Polder interaction between an atom and a conducting wall in cosmic string spacetime
The Casimir-Polder interaction potential is evaluated for a polarizable
microparticle and a conducting wall in the geometry of a cosmic string
perpendicular to the wall. The general case of the anisotropic polarizability
tensor for the microparticle is considered. The corresponding force is a
function of the wall-microparticle and cosmic string-microparticle distances.
Depending on the orientation of the polarizability tensor principal axes the
force can be either attractive or repulsive. The asymptotic behavior of the
Casimir-Polder potential is investigated at large and small separations
compared to the wavelength of the dominant atomic transitions. We show that the
conical defect may be used to control the strength and the sign of the
Casimir-Polder force.Comment: 17 pages, 3 figure
Initial Conditions for Vector Inflation
Recently, a model of inflation using non-minimally coupled massive vector
fields has been proposed. For a particular choice of non-minimal coupling
parameter and for a flat FRW model, the model is reduced to the model of
chaotic inflation with massive scalar field. We study the effect of non-zero
curvature of the universe on the onset of vector inflation. We find that in a
curved universe the dynamics of vector inflation can be different from chaotic
inflation, and the fraction of the initial conditions leading to inflationary
solutions is reduced compared with the chaotic inflation case.Comment: 12 pages, 5 figures, version to be published in JCA
Dynamical dark energy from extra dimensions
We consider multidimensional cosmological model with a higher-dimensional
product manifold M = R x R^{d_0} x H^{d_1}/\Gamma where R^{d_0} is
d_0-dimensional Ricci-flat external (our) space and H^{d_1}/\Gamma is
d_1-dimensional compact hyperbolic internal space. M2-brane solution for this
model has the stage of accelerating expansion of the external space. We apply
this model to explain the late time acceleration of our Universe. Recent
observational data (the Hubble parameter at the present time and the redshift
when the deceleration parameter changes its sign) fix fully all free parameters
of the model. As a result, we find that considered model has too big size of
the internal space at the present time and variation of the effective
four-dimensional fine structure constant strongly exceeds the observational
limits.Comment: 5 pages, 3 figures, LaTex, a few remarks and reference adde
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