205 research outputs found
Go with the Flow, Average Holographic Universe
Gravity is a macroscopic manifestation of a microscopic quantum theory of
space-time, just as the theories of elasticity and hydrodynamics are the
macroscopic manifestation of the underlying quantum theory of atoms. The
connection of gravitation and thermodynamics is long and deep. The observation
that space-time has a temperature for accelerating observers and horizons is
direct evidence that there are underlying microscopic degrees of freedom. The
equipartition of energy, meaning of temperature, in these modes leads one to
anticipate that there is also an entropy associated. When this entropy is
maximized on a volume of space-time, then one retrieves the metric of
space-time (i.e. the equations of gravity, e.g. GR). Since the metric satisfies
the extremum in entropy on the volume, then the volume integral of the entropy
can readily be converted to surface integral, via Gauss's Theorem. This surface
integral is simply an integral of the macroscopic entropy flow producing the
mean entropy holographic principle. This approach also has the added value that
it naturally dispenses with the cosmological constant/vacuum energy problem in
gravity except perhaps for second order quantum effects on the mean surface
entropy.Comment: 14 page
Some Implications of inverse-Compton Scattering of Hot Cocoon Radiation by relativistic jets in Gamma-Ray Bursts
Long Gamma-Ray Bursts (GRB) relativistic jets are surrounded by hot cocoons
which confine jets during their punch out from the progenitor star. These
cocoons are copious sources of X-ray photons that can be and are
inverse-Compton (IC) scattered to MeV--GeV energies by electrons in the
relativistic jet. We provide detailed estimates for IC flux resulting from
various interactions between X-ray photons and the relativistic jet, and
describe what we can learn about GRB jets and progenitor stars from the
detection (or an upper limit) of these IC scattered photons.Comment: 26 pages 7 figures (comments most welcome
Constraints on the topology of the universe from the 2-yr COBE data
The cosmic microwave background (CMB) is a unique probe of cosmological
parameters and conditions. There is a connection between anisotropy in the CMB
and the topology of the Universe. Adopting a universe with the topology of a
3-Torus, or a universe where only harmonics of the fundamental mode are
allowed, and using 2-years of COBE/DMR data, we obtain constraints on the
topology of the Universe. Previous work constrained the topology using the
slope information and the correlation function of the CMB. We obtain more
accurate results by using all multipole moments, avoiding approximations by
computing their full covariance matrix. We obtain the best fit for a cubic
toroidal universe of scale 7200h^{-1} Mpc for n=1. The data set a lower limit
on the cell size of 4320h^{-1} Mpc at 95% confidence and 5880h^{-1} Mpc at 68%
confidence. These results show that the most probable cell size would be around
1.2 times larger than the horizon scale, implying that the 3-Torus topology is
no longer an interesting cosmological model.Comment: Minor revisions to match published version. 14 pages, with 4 figures
included. Color figures and links at
http://www.sns.ias.edu/~angelica/topology.htm
Interstellar Photovoltaics for Exploring Alien Solar Systems
Explore alien solar systems via local star power using interstellar
photovoltaics, tailored for the particular target star for maximum power and
low mass. We consider tailored organic thin-film photovoltaics. Key for
sensing, sending more data back and powering A.I. to send back observational
summaries and interesting events and observations. This plus other technology
developments are necessary for exploring Alien Solar Systems in the not too
distant future.Comment: 14 page
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