20 research outputs found
Natural Neutrino Dark Energy
A new class of neutrino dark energy models is presented. The new models are
characterized by the lack of exotic particles or couplings that violate the
standard model symmetry. It is shown that these models lead to several concrete
predictions for the dark energy equation of state, as well as possible effects
on the cosmic structure formation. These predictions, can be verified (or
disproved) with future experiments. At this point, the strongest constraints on
these models are obtained from big bang nucleosynthesis, and lead to new bounds
on the mass of the lightest neutrino.Comment: 14 pages, 6 figure
Unified Brane Gravity: Cosmological Dark Matter from Scale Dependent Newton Constant
We analyze, within the framework of unified brane gravity, the weak-field
perturbations caused by the presence of matter on a 3-brane. Although deviating
from the Randall-Sundrum approach, the masslessness of the graviton is still
preserved. In particular, the four-dimensional Newton force law is recovered,
but serendipitously, the corresponding Newton constant is shown to be
necessarily lower than the one which governs FRW cosmology. This has the
potential to puzzle out cosmological dark matter. A subsequent conjecture
concerning galactic dark matter follows.Comment: 6 pages, to be published in Phys. Rev.
Hollowgraphy Driven Holography: Black Hole with Vanishing Volume Interior
Hawking-Bekenstein entropy formula seems to tell us that no quantum degrees
of freedom can reside in the interior of a black hole. We suggest that this is
a consequence of the fact that the volume of any interior sphere of finite
surface area simply vanishes. Obviously, this is not the case in general
relativity. However, we show that such a phenomenon does occur in various
gravitational theories which admit a spontaneously induced general relativity.
In such theories, due to a phase transition (one parameter family degenerates)
which takes place precisely at the would have been horizon, the recovered
exterior Schwarzschild solution connects, by means of a self-similar transition
profile, with a novel 'hollow' interior exhibiting a vanishing spatial volume
and a locally varying Newton constant. This constitutes the so-called
'hollowgraphy' driven holography.Comment: Honorable Mention Essay - Gravity Research Foundation (2010
Fermi-bubble bulk and edge analysis reveals dust, cooling breaks, and cosmic-ray diffusion, facilitating a self-consistent model
The full, radio to -ray spectrum of the Fermi bubbles is shown to be
consistent with standard strong-shock electron acceleration at the bubble edge,
without ad-hoc energy cutoffs, if the ambient interstellar radiation is strong;
the -ray cooling break should then have a microwave counterpart,
undetected until now. Indeed, a broadband bubble-edge analysis uncovers a
pronounced downstream dust component, which masked the anticipated GHz
spectral break, and the same overall radio softening consistent with Kraichnan
diffusion previously reported in -rays.Comment: 6 pages, 3 figures, SI; comments welcom
Holographic Entropy Packing inside a Black Hole
If general relativity is spontaneously induced, the black hole limit is
governed by a phase transition which occurs precisely at the would have been
horizon. The exterior Schwarzschild solution then connects with a novel core of
vanishing spatial volume. The Kruskal structure, admitting the exact Hawking
imaginary time periodicity, is recovered, with the conic defect defused at the
origin, rather than at the horizon. The entropy stored inside \textbf{any}
interior sphere is universal, equal to a quarter of its surface area, thus
locally saturating the 't Hooft-Susskind holographic bound. The associated
Komar mass and material energy functions are non-singular.Comment: [V3] accepted to PRL (version shortened, a paragraph on singularity
structure added); 10 pages, no figure