880 research outputs found
Critical velocities and in general theory of relativity
We consider a few thought experiments of radial motion of massive particles
in the gravitational fields outside and inside various celestial bodies: Earth,
Sun, black hole. All other interactions except gravity are disregarded. For the
outside motion there exists a critical value of coordinate velocity : particles with are accelerated by the
field, like Newtonian apples, particles with are
decelerated like photons. Particles moving inside a body with constant density
have no critical velocity; they are always accelerated. We consider also the
motion of a ball inside a tower, when it is thrown from the top (bottom) of the
tower and after classically bouncing at the bottom (top) comes back to the
original point. The total time of flight is the same in these two cases if the
initial proper velocity is equal to .Comment: 13 page
Do neutrino oscillations allow an extra phenomenological parameter?
The quantity introduced recently in the phenomenological description of
neutrino oscillations is in fact not a free parameter, but a fixed number.Comment: 2 pages, LaTeX 2e style articl
Compensation of B-L charge of matter with relic sneutrinos
We consider massless gauge boson connected to B-L charge with and without
compensation to complete the investigation of the gauging of B and L charges.
Relic sneutrinos predicted by SUSY and composite models may compensate B-L
charge of matter. As a consequence of the possible compensation mechanism we
have shown that the available experimental data admit the range of the B-L
interaction constant, 10^{-29} < {\alpha}_{B-L} < 10^{-12}, in addition to
{\alpha}_{B-L} < 10^{-49} obtained without compensation.Comment: 6 page
Constraints on the variability of quark masses from nuclear binding
Based on recent work on nuclear binding, we update and extend the anthropic
constraints on the light quark masses, with results that are more tightly
constrained than previously obtained. We find that heavy nuclei would fall
apart (because the attractive nuclear central potential becomes too weak) if
the sum of the light quark masses m_u+m_d would exceed their physical values by
64% (at 95% confidence level). We summarize the anthropic constraints that
follow from requiring the existence both of heavy atoms and of hydrogen. With
the additional assumption that the quark Yukawa couplings do not vary, these
constraints provide a remarkably tight anthropic window for the Higgs vacuum
expectation value: 0.39 < v/v_physical < 1.64.Comment: 21 pages, 7 figure
A constraint on antigravity of antimatter from precision spectroscopy of simple atoms
Consideration of antigravity for antiparticles is an attractive target for
various experimental projects. There are a number of theoretical arguments
against it but it is not quite clear what kind of experimental data and
theoretical suggestions are involved. In this paper we present straightforward
arguments against a possibility of antigravity based on a few simple
theoretical suggestions and some experimental data. The data are: astrophysical
data on rotation of the Solar System in respect to the center of our galaxy and
precision spectroscopy data on hydrogen and positronium. The theoretical
suggestions for the case of absence of the gravitational field are: equality of
electron and positron mass and equality of proton and positron charge. We also
assume that QED is correct at the level of accuracy where it is clearly
confirmed experimentally
New bounds on the neutrino magnetic moment from the plasma induced neutrino chirality flip in a supernova
The neutrino chirality-flip process under the conditions of the supernova
core is investigated in detail with the plasma polarization effects in the
photon propagator taken into account, in a more consistent way than in earlier
publications. It is shown in part that the contribution of the proton fraction
of plasma is essential. New upper bounds on the neutrino magnetic moment are
obtained: mu_nu < (0.5 - 1.1) 10^{-12} mu_B from the limit on the supernova
core luminosity for nu_R emission, and mu_nu < (0.4 - 0.6) 10^{-12} mu_B from
the limit on the averaged time of the neutrino spin-flip. The best upper bound
on the neutrino magnetic moment from SN1987A is improved by the factor of 3 to
7.Comment: 19 pages, LaTeX, 7 EPS figures, submitted to Journal of Cosmology and
Astroparticle Physic
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