1,405 research outputs found
Long range forces induced by neutrinos at finite temperature
We revisit and extend previous work on neutrino mediated long range forces in
a backround at finite temperature. For Dirac neutrinos, we correct existing
results. We also give new results concerning spin-dependent as well as
spin-independent long range forces associated to Majorana neutrinos. An
interesting outcome of the investigation is that, for both types of neutrinos
whether massless or not, the effect of the relic neutrino heat bath is to
convert those forces into attractive ones in the supra-millimeter scale while
they stay repulsive within the sub-millimeter scale.Comment: 8 pages, Latex, 1 figur
Constraints on Light Pseudoscalars Implied by Tests of the Gravitational Inverse-Square Law
The exchange of light pseudoscalars between fermions leads to a
spin-independent potential in order g^4, where g is the Yukawa
pseudoscalar-fermion coupling constant. This potential gives rise to detectable
violations of both the weak equivalence principle (WEP) and the gravitational
inverse-square law (ISL), even if g is quite small. We show that when
previously derived WEP constraints are combined with those arisingfrom ISL
tests, a direct experimental limit on the Yukawa coupling of light
pseudoscalars to neutrons can be inferred for the first time (g_n^2/4pi < 1.6
\times 10^-7), along with a new (and significantly improved) limit on the
coupling of light pseudoscalars to protons.Comment: 12 pages, Revtex, with 1 Postscript figure (submitted to Physical
Review Letters
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
EC58-704 Efficient Irrigation
Extension Circular 58-704: This is about how to efficiently irrigate your crops
Fichte and Hegel on Recognition
In this paper I provide an interpretation of Hegel’s account of ‘recognition’ (Anerkennung) in the 1802-3 System of Ethical Life as a critique of Fichte’s account of recognition in the 1796-7 Foundations of Natural Right. In the first three sections of the paper I argue that Fichte’s account of recognition in the domain of right is not concerned with recognition as a moral attitude. I then turn, in section four, to a discussion of Hegel’s critique and transformation of Fichte’s conception of recognition. Hegel’s transformation consists, I argue, in the claim that a comprehensive account of recognition in the domain of right must be concerned with recognition as a moral attitude
K-Chameleon and the Coincidence Problem
In this paper we present a hybrid model of k-essence and chameleon, named as
k-chameleon. In this model, due to the chameleon mechanism, the directly strong
coupling between the k-chameleon field and matters (cold dark matters and
baryons) is allowed. In the radiation dominated epoch, the interaction between
the k-chameleon field and background matters can be neglected, the behavior of
the k-chameleon therefore is the same as that of the ordinary k-essence. After
the onset of matter domination, the strong coupling between the k-chameleon and
matters dramatically changes the result of the ordinary k-essence. We find that
during the matter-dominated epoch, only two kinds of attractors may exist: one
is the familiar {\bf K} attractor and the other is a completely {\em new},
dubbed {\bf C} attractor. Once the universe is attracted into the {\bf C}
attractor, the fraction energy densities of the k-chameleon and
dust matter are fixed and comparable, and the universe will undergo
a power-law accelerated expansion. One can adjust the model so that the {\bf K}
attractor do not appear. Thus, the k-chameleon model provides a natural
solution to the cosmological coincidence problem.Comment: Revtex, 17 pages; v2: 18 pages, two figures, more comments and
references added, to appear in PRD, v3: published versio
Gravitational solution to the Pioneer 10/11 anomaly
A fully relativistic modified gravitational theory including a fifth force
skew symmetric field is fitted to the Pioneer 10/11 anomalous acceleration. The
theory allows for a variation with distance scales of the gravitational
constant G, the fifth force skew symmetric field coupling strength omega and
the mass of the skew symmetric field mu=1/lambda. A fit to the available
anomalous acceleration data for the Pioneer 10/11 spacecraft is obtained for a
phenomenological representation of the "running" constants and values of the
associated parameters are shown to exist that are consistent with fifth force
experimental bounds. The fit to the acceleration data is consistent with all
current satellite, laser ranging and observations for the inner planets.Comment: 14 pages, 3 figures, 3 tables. typo's were corrected at Equations (4)
and (12) and a third table including our predictions for the anomalous
perihelion advance of the planets was adde
New two-sided bound on the isotropic Lorentz-violating parameter of modified Maxwell theory
There is a unique Lorentz-violating modification of the Maxwell theory of
photons, which maintains gauge invariance, CPT, and renormalizability.
Restricting the modified-Maxwell theory to the isotropic sector and adding a
standard spin-one-half Dirac particle p^\pm with minimal coupling to the
nonstandard photon \widetilde{\gamma}, the resulting
modified-quantum-electrodynamics model involves a single dimensionless
"deformation parameter," \widetilde{\kappa}_{tr}. The exact tree-level decay
rates for two processes have been calculated: vacuum Cherenkov radiation p^\pm
\to p^\pm \widetilde{\gamma} for the case of positive \widetilde{\kappa}_{tr}
and photon decay \widetilde{\gamma} \to p^+ p^- for the case of negative
\widetilde{\kappa}_{tr}. From the inferred absence of these decays for a
particular high-quality ultrahigh-energy-cosmic-ray event detected at the
Pierre Auger Observatory and an excess of TeV gamma-ray events observed by the
High Energy Stereoscopic System telescopes, a two-sided bound on
\widetilde{\kappa}_{tr} is obtained, which improves by eight orders of
magnitude upon the best direct laboratory bound. The implications of this
result are briefly discussed.Comment: 18 pages, v5: published version in preprint styl
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