3,937 research outputs found
Inflation from R^2 gravity: a new approach using nonlinear electrodynamics
We discuss another approach regarding the inflation from the R^2 theory of
gravity originally proposed by Starobinski. A non-singular early cosmology is
proposed, where, adding a nonlinear electrodynamics Lagrangian to the
high-order action, a bouncing is present and a power-law inflation is obtained.
In the model the Ricci scalar works like an inflaton field.Comment: Definitive version to be published in Astroparticle Physics during
2011, 9 page
Effective temperature, Hawking radiation and quasinormal modes
Parikh and Wilczek have shown that Hawking radiation's spectrum cannot be
strictly thermal. Such a non-strictly thermal character implies that the
spectrum is also not strictly continuous and thus generates a natural
correspondence between Hawking radiation and black hole's quasinormal modes.
This issue endorses the idea that, in an underlying unitary quantum gravity
theory, black holes result highly excited states. We use this key point to
re-analyze the spectrum of black hole's quasinormal modes by introducing a
black hole's effective temperature. Our analysis changes the physical
understanding of such a spectrum and enables a re-examination of various
results in the literature which realizes important modifies on quantum physics
of black holes. In particular, the formula of the horizon's area quantization
and the number of quanta of area are modified becoming functions of the quantum
"overtone" number n. Consequently, Bekenstein-Hawking entropy, its sub-leading
corrections and the number of microstates, i.e. quantities which are
fundamental to realize unitary quantum gravity theory, are also modified. They
become functions of the quantum overtone number too. Previous results in the
literature are re-obtained in the very large n limit.Comment: This essay received an honorable mention in the 2012 Essay
Competition of the Gravity Research Foundation. 11 pages, founded on the
research paper JHEP 1108, 101 (2011), arXiv:1107.533
The YARK theory of gravity can reproduce neither the LIGO's "GW150914 signal" nor the other LIGO's detections of gravitational waves
We show that, based on important reasons, differently from the some recent
claim in the literature, the YARK theory of gravity can reproduce neither the
LIGO's "GW150914 signal" nor the other LIGO's detections of gravitational waves
(GWs).Comment: 4 pages, Concept Paper. Invited contribution accepted for publication
in the Symmetry Special Issue "Gravitational Waves" Edited by Malik Rakhmano
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