5,890 research outputs found
Electromagnetic Zero Point Field as Active Energy Source in the Intergalactic Medium
For over twenty years the possibility that the electromagnetic zero point
field (ZPF) may actively accelerate electromagnetically interacting particles
in regions of extremely low particle density (as those extant in intergalactic
space (IGS) with n < 1 particle/m^3 has been studied and analyzed. This
energizing phenomenon has been one of the few contenders for acceleration of
cosmic rays (CR), particularly at ultrahigh energies. The recent finding by the
AGASA collaboration (Phys. Rev. Lett., 81, 1163, 1998) that the CR energy
spectrum does not display any signs of the Greisen-Zatsepin-Kuzmin cut-off
(that should be present if these CR particles were indeed generated in
localized ultrahigh energies CR sources, as e.g., quasars and other highly
active galactic nuclei), may indicate the need for an acceleration mechanism
that is distributed throughout IGS as is the case with the ZPF. Other
unexplained phenomena that receive an explanation from this mechanism are the
generation of X-ray and gamma-ray backgrounds and the existence of Cosmic
Voids. However recently, a statistical mechanics kind of challenge to the
classical (not the quantum) version of the zero-point acceleration mechanism
has been posed (de la Pena and Cetto, The Quantum Dice, 1996). Here we briefly
examine the consequences of this challenge and a prospective resolution.Comment: 7 pages, no figure
The Klein first integrals in an equilibrium system with electromagnetic, weak, strong and gravitational interactions
The isothermal Tolman condition and the constancy of the Klein potentials
originally expressed for the sole gravitational interaction in a single fluid
are here generalized to the case of a three quantum fermion fluid duly taking
into account the strong, electromagnetic, weak and gravitational interactions.
The set of constitutive equations including the Einstein-Maxwell-Thomas-Fermi
equations as well as the ones corresponding to the strong interaction
description are here presented in the most general relativistic isothermal
case. This treatment represents an essential step to correctly formulate a
self-consistent relativistic field theoretical approach of neutron stars.Comment: To be published by Nuclear Physics
The self-consistent general relativistic solution for a system of degenerate neutrons, protons and electrons in beta-equilibrium
We present the self-consistent treatment of the simplest, nontrivial,
self-gravitating system of degenerate neutrons, protons and electrons in
-equilibrium within relativistic quantum statistics and the
Einstein-Maxwell equations. The impossibility of imposing the condition of
local charge neutrality on such systems is proved, consequently overcoming the
traditional Tolman-Oppenheimer-Volkoff treatment. We emphasize the crucial role
of imposing the constancy of the generalized Fermi energies. A new approach
based on the coupled system of the general relativistic
Thomas-Fermi-Einstein-Maxwell equations is presented and solved. We obtain an
explicit solution fulfilling global and not local charge neutrality by solving
a sophisticated eigenvalue problem of the general relativistic Thomas-Fermi
equation. The value of the Coulomb potential at the center of the configuration
is and the system is intrinsically stable against
Coulomb repulsion in the proton component. This approach is necessary, but not
sufficient, when strong interactions are introduced.Comment: Letter in press, Physics Letters B (2011
Vacuum energy in the presence of a magnetic string with delta function profile
We present a calculation of the ground state energy of massive spinor fields
and massive scalar fields in the background of an inhomogeneous magnetic string
with potential given by a delta function. The zeta functional regularization is
used and the lowest heat kernel coefficients are calculated. The rest of the
analytical calculation adopts the Jost function formalism. In the numerical
part of the work the renormalized vacuum energy as a function of the radius
of the string is calculated and plotted for various values of the strength of
the potential. The sign of the energy is found to change with the radius. For
both scalar and spinor fields the renormalized energy shows no logarithmic
behaviour in the limit , as was expected from the vanishing of the heat
kernel coefficient , which is not zero for other types of profiles.Comment: 30 pages, 10 figure
The Jekyll and Hyde of TREM2
In a recent paper, Gratuze et al. demonstrated a putative neuroprotective role of a key Alzheimer risk variant, TREM2R47H, against tau-mediated neurodegeneration in a mouse model of tauopathy. This study highlights the context-dependent response of microglia, and proposes antagonistic roles of TREM2 in Aβ- versus tau-mediated pathology
Rotational period of WD1953-011 - a magnetic white dwarf with a star spot
WD1953-011 is an isolated, cool (7920 +/- 200K, Bergeron, Legget & Ruiz,
2001) magnetic white dwarf (MWD) with a low average field strength (~70kG,
Maxted et al. 2000) and a higher than average mass (~0.74 M_sun, Bergeron et
al. 2001). Spectroscopic observations taken by Maxted et al. (2000) showed
variations of equivalent width in the Balmer lines, unusual in a low field
white dwarf. Here we present V band photometry of WD1953-011 taken at 7 epochs
over a total of 22 months. All of the datasets show a sinusoidal variation of
approximately 2% peak-to-peak amplitude. We propose that these variations are
due to a star spot on the MWD, analogous to a sunspot, which is affecting the
temperature at the surface, and therefore its photometric magnitude. The
variations have a best-fit period over the entire 22 months of 1.4418 days,
which we interpret as the rotational period of the WD.Comment: (1) University of Southampton, (2) University of Warwick, (3)
University of Nijmegen, (4) Keele University, (5) University of Leicester. 6
pages, 5 figs, accepted MNRA
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