3,139 research outputs found
A classification of scalar field potentials with cosmological scaling solutions
An attractive method of obtaining an effective cosmological constant at the
present epoch is through the potential energy of a scalar field. Considering
models with a perfect fluid and a scalar field, we classify all potentials for
which the scalar field energy density scales as a power-law of the scale factor
when the perfect fluid density dominates. There are three possibilities. The
first two are well known; the much-investigated exponential potentials have the
scalar field mimicking the evolution of the perfect fluid, while for negative
power-laws, introduced by Ratra and Peebles, the scalar field density grows
relative to that of the fluid. The third possibility is a new one, where the
potential is a positive power-law and the scalar field energy density decays
relative to the perfect fluid. We provide a complete analysis of exact
solutions and their stability properties, and investigate a range of possible
cosmological applications.Comment: 8 pages RevTeX file with four figures incorporated (uses RevTeX and
epsf
Attitudes Toward the Non-Traditional Male Role
Attitudes about the non-traditional male role, defined as participation in housework and childcare, and willingness to accept financial assistance from a woman, were investigated. Sex-role identification (determined by the Bem Sex-Role Inventory) and involvement in a serious relationship with a woman were examined as possible factors influencing attitudes about the non-traditional male role. Two hypotheses were investigated and supported: (1) Men in a serious relationship have more positive attitudes toward the non-traditional male role than men not in a serious relationship, and (2) For sex-role identification, feminine men have more positive attitudes about the non-traditional male role than masculine men, and androgynous men have more positive attitudes than either feminine or masculine men. Hours spent doing household chores per week and college class were also correlated with attitudes toward the non-traditional male role
Thawing quintessence with a nearly flat potential
The thawing quintessence model with a nearly flat potential provides a
natural mechanism to produce an equation of state parameter, w, close to -1
today. We examine the behavior of such models for the case in which the
potential satisfies the slow roll conditions: [(1/V)(dV/dphi)]^2 << 1 and
(1/V)(d^2 V/dphi^2) << 1, and we derive the analog of the slow-roll
approximation for the case in which both matter and a scalar field contribute
to the density. We show that in this limit, all such models converge to a
unique relation between 1+w, Omega_phi, and the initial value of
(1/V)(dV/dphi). We derive this relation, and use it to determine the
corresponding expression for w(a), which depends only on the present-day values
for w and Omega_phi. For a variety of potentials, our limiting expression for
w(a) is typically accurate to within delta w < 0.005 for w<-0.9. For redshift z
< 1, w(a) is well-fit by the Chevallier-Polarski-Linder parametrization, in
which w(a) is a linear function of a.Comment: 8 pages, 5 figures, discussion added, references updated, typos
corrected, to appear in Phys. Rev.
User's Guide for ERB 7 SEFDT. Volume 1: User's Guide. Volume 2: Quality Control Report, Year 1
The Nimbus-7 ERB SEFDT Data User's Guide is presented. The guide consists of four subsections which describe: (1) the scope of the data User's Guide; (2) the background on Nimbus-7 Spacecraft and the ERB experiment; (3) the SEFDT data product and processing scenario; and (4) other related products and documents
Predicting Big Bang Deuterium
We present new upper and lower bounds to the primordial abundances of
deuterium and helium-3 based on observational data from the solar system and
the interstellar medium. Independent of any model for the primordial production
of the elements we find (at the 95\% C.L.): and . When combined with
the predictions of standard big bang nucleosynthesis, these constraints lead to
a 95\% C.L. bound on the primordial abundance of deuterium: . Measurements of deuterium absorption in the
spectra of high redshift QSOs will directly test this prediction. The
implications of this prediction for the primordial abundances of helium-4 and
lithium-7 are discussed, as well as those for the universal density of baryons.Comment: Revised version of paper to reflect comments of the referee and reply
to suggestions of Copi, Schramm, and Turner regarding the overall analysis
and treatment of chemical evolution of D and He-3. Best-fit D/H abundance
changes from (2.3 + 3.0 - 1.0)x10^{-5} to (3.5 +2.7 - 1.8) x10^{-5}. See also
hep-ph/950531
The sun's magnetic sector structure
The synoptic appearance of solar magnetic sectors is studied using 454 sector boundaries observed at earth during 1959-1973. The sectors are clearly visible in the photospheric magnetic field. Sector boundaries can be clearly identified as north-south running demarcation lines between regions of persistent magnetic polarity imbalances. These regions extend up to about 35 deg of latitude on both sides of the equator. They generally do not extend into the polar caps. The polar cap boundary can be identified as an east-west demarcation line marking the poleward limit of the sectors. The typical flux imbalance for a magnetic sector is about 4 x 10 to the 21st power Maxwells
Primordial nucleosynthesis as a probe of fundamental physics parameters
We analyze the effect of variation of fundamental couplings and mass scales
on primordial nucleosynthesis in a systematic way. The first step establishes
the response of primordial element abundances to the variation of a large
number of nuclear physics parameters, including nuclear binding energies. We
find a strong influence of the n-p mass difference (for the 4He abundance), of
the nucleon mass (for deuterium) and of A=3,4,7 binding energies (for 3He, 6Li
and 7Li). A second step relates the nuclear parameters to the parameters of the
Standard Model of particle physics. The deuterium, and, above all, 7Li
abundances depend strongly on the average light quark mass hat{m} \equiv
(m_u+m_d)/2. We calculate the behaviour of abundances when variations of
fundamental parameters obey relations arising from grand unification. We also
discuss the possibility of a substantial shift in the lithium abundance while
the deuterium and 4He abundances are only weakly affected.Comment: v2: 34 pages, 2 figures, typo in last GUT scenario corrected, added
discussion and graph of nonlinear behaviour in GUT scenarios, added short
section discussing binding of dineutron and 8Be, refs added, conclusions
unaltered. Accepted for publication, Phys. Rev.
Evaluating movements of opakapaka (Pristipomoides filamentosus) relative to a restricted fishing area by using acoustic telemetry and a depth-constrained estimator of linear home ranges
Networks of no-take fishery reserves have emerged as a tool for managing deepwater fish species. In Hawaii and elsewhere, such areas are used to manage deepwater snapper species. However, little is known regarding the movements of these species relative to protected areas. We used passive acoustic telemetry to track crimson jobfish (Pristipomoides filamentosus), also known as opakapaka, in one of Hawaii’s bottomfish restricted fishing areas to understand the size required for a reserve to protect this species. From January 2017 through January 2018, 179 fish were tagged. Only 10 fish were classified as alive on the basis of movements indicated by detections in tracking data (tracks). For these fish, the median time between the first and last detection of an individual on an acoustic receiver array was 414.5 d with a mean number of detections per individual of 28,321. Linear estimates of home range averaged 3.7 and 6.0 km in conservative and optimistic scenarios, smaller than the median linear habitat dimension of Hawaii’s reserves. Fish were detected within the reserve on 97% or more of the days they were tracked. These results indicate that current reserves in Hawaii are likely sufficient in scale to confer positive biological benefits to opakapaka that reside within their borders
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