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

Summary of Results from COBE

This work presents a summary of major cosmological results from the COBE (Cosmic Background Explorer) satellite mission. The results include a precise measurement of the Cosmic Microwave Background (CMB) radiation intensity, discovery and maps of the CMB anisotropy, large scale observations of the CMB polarization, and the detection and measurement of the diffuse infrared background. This summary was occassioned by and is part of the proceedings for the 3K Cosmology Conference held at Rome in October 1998.Comment: 10 pages, including 2 figure