3,983 research outputs found
Why the Universe Started from a Low Entropy State
We show that the inclusion of backreaction of massive long wavelengths
imposes dynamical constraints on the allowed phase space of initial conditions
for inflation, which results in a superselection rule for the initial
conditions. Only high energy inflation is stable against collapse due to the
gravitational instability of massive perturbations. We present arguments to the
effect that the initial conditions problem {\it cannot} be meaningfully
addressed by thermostatistics as far as the gravitational degrees of freedom
are concerned. Rather, the choice of the initial conditions for the universe in
the phase space and the emergence of an arrow of time have to be treated as a
dynamic selection.Comment: 12 pages, 2 figs. Final version; agrees with accepted version in
Phys. Rev.
Cosmological Avatars of the Landscape II: CMB and LSS Signatures
This is the second paper in the series that confronts predictions of a model
of the landscape with cosmological observations. We show here how the
modifications of the Friedmann equation due to the decohering effects of long
wavelength modes on the wavefunction of the Universe defined on the landscape
leave unique signatures on the CMB spectra and large scale structure (LSS). We
show that the effect of the string corrections is to suppress and
the CMB spectrum at large angles, thereby bringing WMAP and SDSS data for
into agreement. We find interesting features imprinted on the matter
power spectrum : power is suppressed at large scales indicating the
possibility of primordial voids competing with the ISW effect. Furthermore,
power is enhanced at structure and substructure scales, . Our smoking gun for discriminating this proposal from others
with similar CMB and LSS predictions come from correlations between cosmic
shear and temperature anisotropies, which here indicate a noninflationary
channel of contribution to LSS, with unique ringing features of nonlocal
entanglement displayed at structure and substructure scales.Comment: 7 pages, 4 figure
Cosmological Avatars of the Landscape I: Bracketing the SUSY Breaking Scale
We investigate the effects of quantum entanglement between our horizon patch
and others due to the tracing out of long wavelength modes in the wavefunction
of the Universe as defined on a particular model of the landscape. In this, the
first of two papers devoted to this topic, we find that the SUSY breaking scale
is bounded both above {\em and} below: for scale inflation. The lower bound is at least five
orders of magnitude larger than the expected value of this parameter and can be
tested by LHC physics.Comment: 7 pages, 1 figur
A low-altitude satellite interaction study
Two computer programs calculate interaction effects of high speed spacecraft on the environment at altitudes from 90 km to 150 km. EXT program determines fluid field in bodies of arbitrary geometries in transient flow regime. INT program uses EXT output and measures flow conditions inside spacecraft body
'Tilting' the Universe with the Landscape Multiverse: The 'Dark' Flow
The theory for the selection of the initial state of the universe from the
landscape multiverse predicts superhorizon inhomogeneities induced by nonlocal
entanglement of our Hubble volume with modes and domains beyond the horizon.
Here we show these naturally give rise to a bulk flow with correlation length
of order horizon size. The modification to the gravitational potential has a
characteristic scale , and it originates from the
preinflationary remnants of the landscape. The 'tilt' in the potential induces
power to the lowest CMB multipoles, with the dominant contribution being the
dipole and next, the quadrupole. The induced multipoles are aligned
with an axis normal to their alignment plane being oriented along the preferred
frame determined by the dipole. The preferred direction is displayed by the
velocity field of the bulk flow relative to the expansion frame of the
universe. The parameters are tightly constrained thus the derived modifications
lead to robust predictions for testing our theory. The 'dark' flow was recently
discovered by Kashlinsky et al. to be about which seems in good
agreement with our predictions for the induced dipole of order .
Placed in this context, the discovery of the bulk flow by Kashlinsky et al.
becomes even more interesting as it may provide a probe of the preinflationary
physics and a window onto the landscape multiverse.Comment: 7 pgs, 2 fig
Conceptual design study of a six-man solid electrolyte system for oxygen reclamation
A six-man solid electrolyte oxygen regeneration system (SEORS) that will produce 12.5 lbs/day of oxygen has been designed. The SEORS will simultaneously electrolyze both carbon dioxide and water vapor and be suitable for coupling with a carbon dioxide concentration system of either molecular sieve, solid amine or hydrogen depolarized electrochemical type. The total system will occupy approximately 19 cu ft (34.5 in. x .26 in. x 36 in. high) and will weigh approximately 500 pounds. It is estimated that the total electrical power required will be 1783 watts. The system consists of three major components; electrolyzer, hydrogen diffuser, and carbon deposition reactor. There are 108 electrolysis stacks of 12 cells each in the electrolyzer. Only 2/3 of the 108 stacks will be operated at a time; the remainder will be held in reserve. The design calls for 96 palladium membranes for hydrogen removal to give 60 percent redundancy. Four carbon deposition reactors are employed. The iron catalyst tube in each reactor weighs 7.1 lb and 100 percent redundancy is allowed
Inflaton Decay in an Alpha Vacuum
We study the alpha vacua of de Sitter space by considering the decay rate of
the inflaton field coupled to a scalar field placed in an alpha vacuum. We find
an {\em alpha dependent} Bose enhancement relative to the Bunch-Davies vacuum
and, surprisingly, no non-renormalizable divergences. We also consider a
modified alpha dependent time ordering prescription for the Feynman propagator
and show that it leads to an alpha independent result. This result suggests
that it may be possible to calculate in any alpha vacuum if we employ the
appropriate causality preserving prescription.Comment: 16 pages, 1 figure, Revtex 4 preprin
The Size Distribution of Trans-Neptunian Bodies
[Condensed] We search 0.02 deg^2 for trans-Neptunian objects (TNOs) with
m<=29.2 (diameter ~15 km) using the ACS on HST. Three new objects are
discovered, roughly 25 times fewer than expected from extrapolation of the
differential sky density Sigma(m) of brighter objects. The ACS and other recent
TNO surveys show departures from a power law size distribution. Division of the
TNO sample into ``classical Kuiper belt'' (CKB) and ``Excited'' samples reveals
that Sigma(m) differs for the two populations at 96% confidence. A double power
law adequately fits all data. Implications include: The total mass of the CKB
is ~0.010 M_Earth, only a few times Pluto's mass, and is predominately in the
form of ~100 km bodies. The mass of Excited objects is perhaps a few times
larger. The Excited class has a shallower bright-end size distribution; the
largest objects, including Pluto, comprise tens of percent of the total mass
whereas the largest CKBOs are only ~2% of its mass. The predicted mass of the
largest Excited body is close to the Pluto mass; the largest CKBO is ~60 times
less massive. The deficit of small TNOs occurs for sizes subject to disruption
by present-day collisions, suggesting extensive depletion by collisions. Both
accretion and erosion appearing to have proceeded to more advanced stages in
the Excited class than the CKB. The absence of distant TNOs implies that any
distant (60 AU) population must have less than the CKB mass in the form of
objects 40 km or larger. The CKB population is sparser than theoretical
estimates of the required precursor population for short period comets, but the
Excited population could be a viable precursor population.Comment: Revised version accepted to the Astronomical Journal. Numerical
results are very slightly revised. Implications for the origins of
short-period comets are substantially revised, and tedious material on
statistical tests has been collected into a new Appendi
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