71,432 research outputs found
Phantom Energy and the Cosmic Horizon: Rh is still not a horizon!
There has been a recent spate of papers on the Cosmic Horizon, an apparently
fundamental, although unrecognised, property of the universe. The
misunderstanding of this horizon, it is claimed, demonstrates that our
determination of the cosmological makeup of the universe is incorrect, although
several papers have pointed out key flaws in these arguments. Here, we identify
additional flaws in the most recent claims of the properties of the Cosmic
Horizon in the presence of phantom energy, simply demonstrating that it does
not act as a horizon, and that its limiting of our view of the universe is a
trivial statement.Comment: 4 pages, 1 figure. Accepted for publication in MNRAS Letter
Lewis F. Powell Jr. to John D. Feerick
Letter from Supreme Court Justice Lewis F. Powell Jr. (1972-1987) to Dean John D. Feerick, regarding his scholarly article on presidential inability.https://ir.lawnet.fordham.edu/twentyfifth_amendment_correspondence/1016/thumbnail.jp
Photoelectron spectrometer with means for stabilizing sample surface potential
An improved X-ray photoelectron spectrometer is disclosed, which includes circuit means to determine the surface potential of a sample, e.g., an insulator. The circuit means comprise an electron gun, whose potential is modulated at a preselected frequency above and below a selected potential with respect to the spectrometer common potential, e.g., ground. The beam of electrons is directed to the sample surface. The sample's surface potential is offset by an offset power supply with respect to the spectrometer common potential until the ac current which flows through the sample reaches a peak amplitude. A lock-in amplifier is included to measure the ac current in phase with the modulating frequency
Seeing Star Formation Regions with Gravitational Microlensing
We qualitatively study the effects of gravitational microlensing on our view
of unresolved extragalactic star formation regions. Using a general
gravitational microlensing configuration, we perform a number of simulations
that reveal that specific imprints of the star forming region are imprinted,
both photometrically and spectroscopically, upon observations. Such
observations have the potential to reveal the nature and size of these star
forming regions, through the degree of variability observed in a monitoring
campaign, and hence resolve the star formation regions in distant galaxies
which are too small to be probed via more standard techniques.Comment: 7 pages, 8 figures, ApJ accepte
Producing the Deuteron in Stars: Anthropic Limits on Fundamental Constants
Stellar nucleosynthesis proceeds via the deuteron (D), but only a small
change in the fundamental constants of nature is required to unbind it. Here,
we investigate the effect of altering the binding energy of the deuteron on
proton burning in stars. We find that the most definitive boundary in parameter
space that divides probably life-permitting universes from probably
life-prohibiting ones is between a bound and unbound deuteron. Due to neutrino
losses, a ball of gas will undergo rapid cooling or stabilization by electron
degeneracy pressure before it can form a stable, nuclear reaction-sustaining
star. We also consider a less-bound deuteron, which changes the energetics of
the and reactions. The transition to endothermic and
reactions, and the resulting beta-decay instability of the deuteron, do not
seem to present catastrophic problems for life.Comment: 19 pages, 5 figures. Accepted to JCAP. Revised to match the published
version; corrected to better take into account free neutron
FOOD DISTRIBUTION RESEARCH PRIORITIES TO ALLOW MAJOR IMPROVEMENTS IN TOTAL SYSTEM PRODUCTIVITY BY 1985: FOOD RETAILING
Agricultural and Food Policy,
Microlensing of Broad Absorption Line Quasars
The physical nature of the material responsible for the high--velocity,
broad-absorption line features seen in a small fraction of quasar spectra has
been the subject of debate since their discovery. This has been especially
compounded by the lack of observational probes of the absorbing region. In this
paper we examine the role of ``microlenses'' in external galaxies on observed
variability in the profiles of broad absorption lines in multiply-imaged
quasars. Utilizing realistic models for both the broad absorption line region
and the action of an ensemble of microlensing masses, we demonstrate that stars
at cosmological distances can provide an important probe of the physical state
and structure of material at the heart of these complex systems. Applying these
results to the macrolensed BAL quasar system, H1413+117, the observed spectral
variations are readily reproduced, but without the fine-tuning requirements of
earlier studies which employ more simplistic models.Comment: 7 pages, 4 figures (included), Latex (mn.sty), Submitted to MNRA
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