10,245 research outputs found
Getting a start in dairying in Alaska
Dairying in Alaska probably will always be confined to areas where milk can reach city markets readily. The demand £or fresh milk, even at present prices, exceeds the supply. Probably the dairy farmer always will be able to produce milk in competition with fluid mlik shipped in from the States if he is a good manager and has high producing cows. A farmer with low producing cows can show a profit at present prices, but if the price of milk dropped two dollars or more per hundred, he would have a tough time making both ends meet. It is doubtful if other dairy products can be produced in Alaska to compete with stateside prices
About the propagation of the Gravitational Waves in an asymptotically de-Sitter space: Comparing two points of view
We analyze the propagation of gravitational waves (GWs) in an asymptotically
de-Sitter space by expanding the perturbation around Minkowski and introducing
the effects of the Cosmological Constant (), first as an additional
source (de-Donder gauge) and after as a gauge effect (-gauge). In both
cases the inclusion of the Cosmological Constant impedes the
detection of a gravitational wave at a distance larger than
, where
and f and are the frequency and
strain of the wave respectively. We demonstrate that is just a
confirmation of the Cosmic No hair Conjecture (CNC) already explained in the
literature.Comment: Accepted for publication in MPL
Sideband cooling while preserving coherences in the nuclear spin state in group-II-like atoms
We propose a method for laser cooling group-II-like atoms without changing
the quantum state of their nuclear spins, thus preserving coherences that are
usually destroyed by optical pumping. As group-II-like atoms have a
closed-shell ground state, nuclear spin and electronic degrees of freedom are
decoupled, allowing for independent manipulation. The hyperfine interaction
that couples these degrees of freedom in excited states can be suppressed
through the application of external magnetic fields. Our protocol employs
resolved-sideband cooling on the forbidden clock transition, , with quenching via coupling to the rapidly decaying state,
deep in the Paschen-Back regime. This makes it possible to laser cool neutral
atomic qubits without destroying the quantum information stored in their
nuclear spins, as shown in two examples, Yb and Sr.Comment: 4 pages, 3 figures v4: minor changes in text, changes in the
references, published versio
Resummed QCD Power Corrections to Nuclear Shadowing
We calculate and resum a perturbative expansion of nuclear enhanced power
corrections to the structure functions measured in deeply inelastic scattering
of leptons on a nuclear target. Our results for the Bjorken -, - and
-dependence of nuclear shadowing in and the nuclear
modifications to , obtained in terms of the QCD factorization
approach, are consistent with the existing data. We demonstrate that the
low- behavior of these data and the measured large longitudinal structure
function point to a critical role for the power corrections when compared to
other theoretical approaches.Comment: 4 pages, 3 figures, uses RevTeX 4. As published in Phys.Rev.Let
Matrix General Relativity: A New Look at Old Problems
We develop a novel approach to gravity that we call `matrix general
relativity' (MGR) or `gravitational chromodynamics' (GCD or GQCD for quantum
version). Gravity is described in this approach not by one Riemannian metric
(i.e. a symmetric two-tensor field) but by a multiplet of such fields, or by a
matrix-valued symmetric two-tensor field that satisfies certain conditions. We
define the matrix extensions of standard constructions of differential geometry
including connections and curvatures, and finally, an invariant functional of
the new field that reduces to the standard Einstein action functional in the
commutative (diagonal) case. Our main idea is the analogy with Yang-Mills
theory (QCD and Standard Model). We call the new degrees of freedom of gravity
associated with the matrix structure `gravitational color' or simply
`gravicolor' and introduce a new gauge symmetry associated with this degree of
freedom. As in the Standard Model there are two possibilities. First of all, it
is possible that at high energies (say at Planckian scale) this symmetry is
exact (symmetric phase), but at low energies it is badly broken, so that one
tensor field remains massless (and gives general relativity) and the other ones
become massive with the masses of Planckian scale. Second possibilty is that
the additional degrees of freedom of gravitational field are confined within
the Planckian scale. What one sees at large distances are singlets (invariants)
of the new gauge symmetry.Comment: 25 page
Spectra and Diagnostics for the Direct Detection of Wide-Separation Extrasolar Giant Planets
We calculate as a function of orbital distance, mass, and age the theoretical
spectra and orbit-averaged planet/star flux ratios for representative
wide-separation extrasolar giant planets (EGPs) in the optical, near-infrared,
and mid-infrared. Stellar irradiation of the planet's atmosphere and the
effects of water and ammonia clouds are incorporated and handled in a
consistent fashion. We include predictions for 12 specific known EGPs. In the
process, we derive physical diagnostics that can inform the direct EGP
detection and remote sensing programs now being planned or proposed.
Furthermore, we calculate the effects of irradiation on the spectra of a
representative companion brown dwarf as a function of orbital distance.Comment: submitted to the Astrophysical Journal, 19 pages, 11 color figure
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