143 research outputs found
Is the physical vacuum a preferred frame ?
It is generally assumed that the physical vacuum of particle physics should
be characterized by an energy momentum tensor in such a way to preserve exact
Lorentz invariance. On the other hand, if the ground state were characterized
by its energy-momentum vector, with zero spatial momentum and a non-zero
energy, the vacuum would represent a preferred frame. Since both theoretical
approaches have their own good motivations, we propose an experimental test to
decide between the two scenarios.Comment: 12 pages, no figure
Relativistic Kinetics of Phonon Gas in Superfluids
The relativistic kinetic theory of the phonon gas in superfluids is
developed. The technique of the derivation of macroscopic balance equations
from microscopic equations of motion for individual particles is applied to an
ensemble of quasi-particles. The necessary expressions are constructed in terms
of a Hamilton function of a (quasi-)particle. A phonon contribution into
superfluid dynamic parameters is obtained from energy-momentum balance
equations for the phonon gas together with the conservation law for superfluids
as a whole. Relations between dynamic flows being in agreement with results of
relativistic hydrodynamic consideration are found. Based on the kinetic
approach a problem of relativistic variation of the speed of sound under phonon
influence at low temperature is solved.Comment: 23 pages, Revtex fil
Spinning particles in Schwarzschild-de Sitter space-time
After considering the reference case of the motion of spinning test bodies in
the equatorial plane of the Schwarzschild space-time, we generalize the results
to the case of the motion of a spinning particle in the equatorial plane of the
Schwarzschild-de Sitter space-time. Specifically, we obtain the loci of turning
points of the particle in this plane. We show that the cosmological constant
affect the particle motion when the particle distance from the black hole is of
the order of the inverse square root of the cosmological constant.Comment: 8 pages, 5 eps figures, submitted to Gen.Rel.Gra
Stress tensor fluctuations in de Sitter spacetime
The two-point function of the stress tensor operator of a quantum field in de
Sitter spacetime is calculated for an arbitrary number of dimensions. We assume
the field to be in the Bunch-Davies vacuum, and formulate our calculation in
terms of de Sitter-invariant bitensors. Explicit results for free minimally
coupled scalar fields with arbitrary mass are provided. We find long-range
stress tensor correlations for sufficiently light fields (with mass m much
smaller than the Hubble scale H), namely, the two-point function decays at
large separations like an inverse power of the physical distance with an
exponent proportional to m^2/H^2. In contrast, we show that for the massless
case it decays at large separations like the fourth power of the physical
distance. There is thus a discontinuity in the massless limit. As a byproduct
of our work, we present a novel and simple geometric interpretation of de
Sitter-invariant bitensors for pairs of points which cannot be connected by
geodesics.Comment: 35 pages, 4 figure
Semiclassical relations and IR effects in de Sitter and slow-roll space-times
We calculate IR divergent graviton one-loop corrections to scalar correlators
in de Sitter space, and show that the leading IR contribution may be reproduced
via simple semiclassical consistency relations. One can likewise use such
semiclassical relations to calculate leading IR corrections to correlators in
slow-roll inflation. The regulated corrections shift the tensor/scalar ratio
and consistency relation of single field inflation, and non-gaussianity
parameters averaged over very large distances. For inflation of sufficient
duration, for example arising from a chaotic inflationary scenario, these
corrections become of order unity. First-order corrections of this size
indicate a breakdown of the perturbative expansion, and suggest the need for a
non-perturbative description of the corresponding regime. This is analogous to
a situation argued to arise in black hole evolution, and to interfere with a
sharp perturbative calculation of "missing information" in Hawking radiation.Comment: 32 pages, 2 figures; v2: running of spectral index included and other
minor changes; v3: minor changes to agree with published versio
Single gluino production in the R-parity lepton number violating MSSM at the LHC
We examine the -violating signal of single gluino production
associated with a charged lepton or neutrino at the large hadron collider
(LHC), in the model of R-parity relaxed supersymmetric model. If the parameters
in the supersymmetric interactions are not too small, and the
mass of gluino is considered in the range from several GeV (as the Lightest
Supersymmetric Particle) to 800 GeV, the cross section of the single gluino
production via Drell-Yan processes can be in the order of
femto barn, and that via gluon fusion in the order of femto
barn. If the gluino decay can be well detected in the CERN LHC, this process
provides a prospective way to probe supersymmetry and violation.Comment: LaTex, 22 pages, 5 EPS file
The ASSURE study: HIV-1 suppression is maintained with bone and renal biomarker improvement 48 weeks after ritonavir discontinuation and randomized switch to abacavir/lamivudine+atazanavir
Objectives: HIV treatment guidelines endorse switching or simplification of antiretroviral therapy in therapy-experienced patients with suppressed viraemia; ritonavir discontinuation may also enhance tolerability and reduce long-term adverse events (AEs). This open-label, multicentre, noninferiority study enrolled HIV-1-infected, treatment-experienced adults with confirmed HIV-1 RNA≤75 HIV-1 RNA copies/mL currently receiving tenofovir/emtricitabine+atazanavir/ritonavir (TDF/FTC+ATV/r) for ≥6 months with no reported history of virological failure. Methods: Participants were randomized 1:2 to continue current treatment or switch to abacavir/lamivudine + atazanavir (ABC/3TC+ATV). Endpoints included the proportion of participants with HIV-1 RNA<50 copies/mL by time to loss of virological response (TLOVR), AEs, fasting lipids, and inflammatory, coagulation, bone and renal biomarkers. Results: After 48 weeks, 76% (152 of 199) of ABC/3TC+ATV-treated and 79% (77 of 97) of TDF/FTC+ATV/r-treated participants had HIV-1 RNA<50 copies/mL (TLOVR; P=0.564). Other efficacy analyses yielded similar results. Rates of new grade 2-4 AEs were 45% in both groups, but an excess of hyperbilirubinaemia made the rate of treatment-emergent grade 3-4 laboratory abnormalities higher with TDF/FTC+ATV/r (36%) compared with ABC/3TC+ATV (19%). Most fasting lipid levels remained stable over time; high-density lipoprotein (HDL) cholesterol increased modestly in ABC/3TC+ATV-treated participants. Bone and renal biomarkers improved significantly between baseline and week 48 in participants taking ABC/3TC+ATV and were stable in participants taking TDF/FTC+ATV/r. No significant changes occurred in any inflammatory or coagulation biomarker within or between treatment groups. Conclusions: The ABC/3TC+ATV treatment-switch group had similar viral suppression rates up to 48 weeks to the TDF/FTC+ATV/r comparator group, with lower rates of moderate- to high-grade hyperbilirubinaemia and improvements in bone and renal biomarkers
Thermodynamic Gravity and the Schrodinger Equation
We adopt a 'thermodynamical' formulation of Mach's principle that the rest
mass of a particle in the Universe is a measure of its long-range collective
interactions with all other particles inside the horizon. We consider all
particles in the Universe as a 'gravitationally entangled' statistical ensemble
and apply the approach of classical statistical mechanics to it. It is shown
that both the Schrodinger equation and the Planck constant can be derived
within this Machian model of the universe. The appearance of probabilities,
complex wave functions, and quantization conditions is related to the
discreetness and finiteness of the Machian ensemble.Comment: Minor corrections, the version accepted by Int. J. Theor. Phy
Cosmic Background Bose Condensation (CBBC)
Degeneracy effects for bosons are more important for smaller particle mass, smaller temperature and higher number density. Bose condensation requires that particles be in the same lowest energy quantum state. We propose a cosmic background Bose condensation, present everywhere, with its particles having the lowest quantum energy state, A c/lambda, with lambda about the size of the visible universe, and therefore unlocalized. This we identify with the quantum of the self gravitational potential energy of any particle, and with the bit of information of minimum energy. The entropy of the universe (similar to 10(122) bits) has the highest number density (similar to 10(36) bits/cm(3)) of particles inside the visible universe, the smallest mass, similar to 10(-66) g, and the smallest temperature, similar to 10(-29) K. Therefore it is the best candidate for a Cosmic Background Bose Condensation (CBBC), a completely calmed fluid, with no viscosity, in a superfluidity state, and possibly responsible for the expansion of the universe.Alfonso-Faus, A.; Fullana Alfonso, MJ. (2013). Cosmic Background Bose Condensation (CBBC). Astrophysics and Space Science. 347(1):193-196. doi:10.1007/s10509-013-1500-8S1931963471Alfonso-Faus, A.: Universality of the self gravitational potential energy of any fundamental particle. Astrophys. Space Sci. 337, 363 (2010a)Alfonso-Faus, A.: The case for the Universe to be a quantum black hole. Astrophys. Space Sci. 325, 113 (2010b)Alfonso-Faus, A.: Galaxies: kinematics as a proof of the existence of a universal field of minimum acceleration. arXiv:0708.0308 (2010c, preprint)Alfonso-Faus, A.: Quantum gravity and information theories linked by the physical properties of the bit. arXiv:1105.3143 (2011, preprint)Anderson, J.D., et al.: Indication, from Pioneer 10/11, Galileo, and Ulysses data, of an apparent anomalous, weak, long-range acceleration. Phys. Rev. Lett. 81, 2858 (1998)Bekenstein, J.D.: Phys. Rev. D 23(2), 287 (1981)Bérut, A., et al.: Experimental verification of Landauer’s principle linking information and thermodynamics. Nature 483, 187 (2012)Drees, M., Chung-Lin, S.: Theoretical interpretation of experimental data from direct dark matter detection. J. Cosmol. Astropart. Phys. 0706, 011 (2007)Eisberg, R., Resnick, R.: Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles, 2nd edn. Wiley, New York (1985)Funo, K., Watanabe, Y., Ueda, M.: Thermodynamic work gain from entanglement. arXiv:1207.6872 [quant-ph] (2012, preprint)Hawking, S.W.: Black hole explosions? Nature 248, 30 (1974)Landauer, R.: Irreversibility and heat generation in the computing process. IBM J. Res. Dev. 5, 183 (1961)Landauer, R.: Dissipation and noise immunity in computation and communication. Nature 335, 779 (1988)Lloyd, S.: Computational capacity of the universe. Phys. Rev. Lett. 88, 237901 (2002)Misner, C.W., Thorne, K.S., Wheeler, J.A.: Gravitation. Freeman, Reading (1973), p. 466 (“Why the energy of the gravitational field cannot be localized”)Scarpa, R., Falomo, R.: Testing Newtonian gravity in the low acceleration regime with globular clusters: the case of omega Centauri revisited. Astron. Astrophys. 523, A43 (2010)Sivaram, C.: Cosmological and quantum constraint on particle masses. Am. J. Phys. 50, 279 (1982)Susskind, L.: The World as a hologram. J. Math. Phys. 36, 6377 (1995)’t Hooft, G.: Dimensional reduction in quantum gravity. arXiv:gr-qc/9310026 (1993, preprint)Toyabe, S., et al.: Experimental demonstration of information-to-energy conversion and validation of the generalized Jarzynski equality. Nat. Phys. 6, 988 (2010)Unruh, W.G.: Notes on black-hole evaporation. Phys. Rev. D, Part. Fields 14(4), 870 (1976)Weinberg, S.: Gravitation and Cosmology: Principles and Applications of the General Theory of Relativity p. 619. Wiley, New York (1972
Filtering out the cosmological constant in the Palatini formalism of modified gravity
According to theoretical physics the cosmological constant (CC) is expected
to be much larger in magnitude than other energy densities in the universe,
which is in stark contrast to the observed Big Bang evolution. We address this
old CC problem not by introducing an extremely fine-tuned counterterm, but in
the context of modified gravity in the Palatini formalism. In our model the
large CC term is filtered out, and it does not prevent a standard cosmological
evolution. We discuss the filter effect in the epochs of radiation and matter
domination as well as in the asymptotic de Sitter future. The final expansion
rate can be much lower than inferred from the large CC without using a
fine-tuned counterterm. Finally, we show that the CC filter works also in the
Kottler (Schwarzschild-de Sitter) metric describing a black hole environment
with a CC compatible to the future de Sitter cosmos.Comment: 22 pages, 1 figure, discussion extended, references added, accepted
by Gen.Rel.Gra
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