11,380 research outputs found
Effects of Bose-Einstein Condensation on forces among bodies sitting in a boson heat bath
We explore the consequences of Bose-Einstein condensation on
two-scalar-exchange mediated forces among bodies that sit in a boson gas. We
find that below the condensation temperature the range of the forces becomes
infinite while it is finite at temperatures above condensation.Comment: 10 pages, 2 figure
Casimir-Polder forces in the presence of the cosmic photon heat bath
We study the effect of a photon background at finite temperature on the
Van der Waals interactions among neutral bodies. It turns out that the
long-range Casimir-Polder force is unaffected for distances much less than
and strongly enhanced for distances much above .Comment: 8 pages, 2 figure
Suppressing Super-Horizon Curvature Perturbations?
We consider the possibility of suppressing superhorizon curvature
perturbations after the end of the ordinary slow-roll inflationary stage. This
is the opposite of the curvaton limit. We assume that large curvature
perturbations are created by the inflaton and investigate if they can be
diluted or suppressed by a second very homogeneous field which starts to
dominate the energy density of the universe shortly after the end of inflation.
We show explicit that the gravitational sourcing of inhomogeneities from the
more inhomogeneous fluid to the more homogeneous fluid makes the suppression
difficult if not impossible to achieve.Comment: 10 pages, 1 figure. Important revision. Conclusions more negativ
Correlated Primordial Perturbations in Light of CMB and LSS Data
We use cosmic microwave background (CMB) and large-scale structure data to
constrain cosmological models where the primordial perturbations have both an
adiabatic and a cold dark matter (CDM) isocurvature component. We allow for a
possible correlation between the adiabatic and isocurvature modes, and for
different spectral indices for the power in each mode and for their
correlation. We do a likelihood analysis with 11 independent parameters. We
discuss the effect of choosing the pivot scale for the definition of amplitude
parameters. The upper limit for the isocurvature fraction is 18% around a pivot
scale k = 0.01 Mpc^{-1}. For smaller pivot wavenumbers the limit stays about
the same. For larger pivot wavenumbers, very large values of the isocurvature
spectral index are favored, which makes the analysis problematic, but larger
isocurvature fractions seem to be allowed. For large isocurvature spectral
indices n_iso > 2 a positive correlation between the adiabatic and isocurvature
mode is favored, and for n_iso < 2 a negative correlation is favored. The upper
limit to the nonadiabatic contribution to the CMB temperature variance is 7.5%.
Of the standard cosmological parameters, determination of the CDM density
and the sound horizon angle (or the Hubble constant )
are affected most by a possible presence of a correlated isocurvature
contribution. The baryon density nearly retains its ``adiabatic
value''.Comment: 20 pages, 21 figures (many in color
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