1,679 research outputs found
Exponential-Potential Scalar Field Universes I: The Bianchi I Models
We obtain a general exact solution of the Einstein field equations for the
anisotropic Bianchi type I universes filled with an exponential-potential
scalar field and study their dynamics. It is shown, in agreement with previous
studies, that for a wide range of initial conditions the late-time behaviour of
the models is that of a power-law inflating FRW universe. This property, does
not hold, in contrast, when some degree of inhomogeneity is introduced, as
discussed in our following paper II.Comment: 16 pages, Plain LaTeX, 1 Figure to be sent on request, to appear in
Phys. Rev.
Psychological flexibility mediates the relation between self-concealment and negative psychological outcomes.
Consisting of two cross-sectional studies, the present study investigated whether psychological flexibility mediates the relations between self-concealment and negative psychological outcomes. Study 1 examined whether psychological flexibility mediates the relations between self-concealment and emotional distress in stressful interpersonal situations. In addition to replicating results of Study 1, Study 2 investigated whether psychological flexibility mediates the relationship between self-concealment and general psychological ill-health. Psychological flexibility was found to mediate the relation between self-concealment and emotional distress in stressful interpersonal settings and to partially mediate the relationship between self-concealment and general psychological ill-health
The effects of cognitive defusion and thought distraction on emotional discomfort and believability of negative self-referential thoughts
Previous research has shown that rapid vocal repetition of a one-word version of negative self-referential thought reduces the stimulus functions (e.g., emotional discomfort and believability) associated with that thought. The present study compares the effects of that defusion strategy with thought distraction and distraction-based experimental control tasks on a negative self-referential thought. Non-clinical undergraduates were randomly assigned to one of three protocols. The cognitive defusion condition reduced the emotional discomfort and believability of negative self-referential thoughts significantly greater than comparison conditions. Favorable results were also found for the defusion technique with participants with elevated depressive symptoms
Reconstruction of Scalar Potentials in Induced Gravity and Cosmology
We develop a technique for the reconstruction of the potential for a scalar
field in cosmological models based on induced gravity. The potentials
reproducing cosmological evolutions driven by barotropic perfect fluids, a
cosmological constant, a Chaplygin gas and a modified Chaplygin gas are
constructed explicitly.Comment: 14 pages, no figures. Final version published in PL
High-Mass Cloud Cores in the eta Carinae Giant Molecular Cloud
We carried out an unbiased survey for massive dense cores in the giant
molecular cloud associated with eta Carinae with the NANTEN telescope in 12CO,
13CO, and C18O 1-0 emission lines. We identified 15 C18O cores. Two of the 15
cores are associated with IRAS point sources whose luminosities are larger than
10^4 Lo, which indicates that massive star formation is occuring within these
cores. Five cores including the two with IRAS sources are associated with MSX
point sources. We detected H13CO+ (1-0) emission toward 4 C18O cores, one of
which is associated with neither IRAS nor MSX point sources. This core shows
the presence of a bipolar molecular outflow in 12CO (2-1), which indicates that
star formation is also occuring in the core. In total, six C18O cores out of 15
are experienced star formation, and at least 2 of 15 are massive-star forming
cores in the eta Car GMC. We found that massive star formation occurs
preferentially in cores with larger column density, mass, number density, and
smaller ratio of virial mass to LTE mass Mvir/M. We also found that the cores
in the eta Car GMC are characterized by large line width and Mvir/M on average
compared to the cores in other GMCs. We investigated the origin of a large
amount of turbulence in the eta Car GMC. We propose the possibility that the
large turbulence was pre-existing when the GMC was formed, and is now
dissipating. Mechanisms such as multiple supernova explosions in the Carina
flare supershell may have contributed to form a GMC with a large amount of
turbulence.Comment: 41 pages, including 11 fugures and 9 tables. Accepted by ApJ. Author
changed. Paper with high resolution figures is available at
http://astrol.cias.osakafu-u.ac.jp/~yonekura/work/paper/etaCar
Lamin activity is essential for nuclear envelope assembly in a Drosophila embryo cell-free extract.
Solution generating in scalar-tensor theories with a massless scalar field and stiff perfect fluid as a source
We present a method for generating solutions in some scalar-tensor theories
with a minimally coupled massless scalar field or irrotational stiff perfect
fluid as a source. The method is based on the group of symmetries of the
dilaton-matter sector in the Einstein frame. In the case of Barker's theory the
dilaton-matter sector possesses SU(2) group of symmetries. In the case of
Brans-Dicke and the theory with "conformal coupling", the dilaton- matter
sector has as a group of symmetries. We describe an explicit
algorithm for generating exact scalar-tensor solutions from solutions of
Einstein-minimally-coupled-scalar-field equations by employing the nonlinear
action of the symmetry group of the dilaton-matter sector. In the general case,
when the Einstein frame dilaton-matter sector may not possess nontrivial
symmetries we also present a solution generating technique which allows us to
construct exact scalar-tensor solutions starting with the solutions of
Einstein-minimally-coupled-scalar-field equations. As an illustration of the
general techniques, examples of explicit exact solutions are constructed. In
particular, we construct inhomogeneous cosmological scalar-tensor solutions
whose curvature invariants are everywhere regular in space-time. A
generalization of the method for scalar-tensor-Maxwell gravity is outlined.Comment: 10 pages,Revtex; v2 extended version, new parts added and some parts
rewritten, results presented more concisely, some simple examples of
homogeneous solutions replaced with new regular inhomogeneous solutions,
typos corrected, references and acknowledgements added, accepted for
publication in Phys.Rev.
A multi-wavelength study of the unidentified TeV gamma-ray source HESS J1626-490
HESS J1626-490, so far only detected with the H.E.S.S. array of imaging
atmospheric Cherenkov telescopes, could not be unambiguously identified with
any source seen at lower energies. Therefore, we analyzed data from an archival
XMM-Newton observation, pointed towards HESS J1626-490, to classify detected
X-ray point-sources according to their spectral properties and their
near-infrared counterparts from the 2MASS catalog. Furthermore, we
characterized in detail the diffuse X-ray emission from a region compatible
with the extended VHE signal. To characterize the Interstellar Medium
surrounding HESS J1626-490 we analyzed CO(J=1-0) molecular line data
from the NANTEN Galactic plane survey, HI data from the Southern Galactic Plane
Survey and Spitzer data from the GLIMPSE and MIPSGAL surveys. None of the
detected X-ray point sources fulfills the energetic requirements to be
considered as the synchrotron radiation (SR) counterpart to the VHE source
assuming an Inverse Compton (IC) emission scenario. We did not detect any
diffuse X-ray excess emission originating from the region around HESS J1626-490
above the Galactic Background and the derived upper limit for the total X-ray
flux disfavors a purely leptonic emission scenario for HESS J1626-490. We found
a good morphological match between molecular and atomic gas in the -27km/s to
-18km/s line-of-sight velocity range and HESS J1626-490. The cloud has a mass
of 1.8M and is located at a mean kinematic distance of
= 1.8 kpc. Furthermore, we found a density depression in the HI gas at a
similar distance which is spatially consistent with the SNR G335.2+00.1. We
discuss various scenarios for the VHE emission, including the CO molecular
cloud being a passive target for cosmic ray protons accelerated by the nearby
SNR G335.2+00.1.Comment: 9 pages, 10 figures, A&A in press, updated to the final versio
On the Asymptotic Behaviour of Cosmological Models in Scalar-Tensor Theories of Gravity
We study the qualitative properties of cosmological models in scalar-tensor
theories of gravity by exploiting the formal equivalence of these theories with
general relativity minimally coupled to a scalar field under a conformal
transformation and field redefinition. In particular, we investigate the
asymptotic behaviour of spatially homogeneous cosmological models in a class of
scalar-tensor theories which are conformally equivalent to general relativistic
Bianchi cosmologies with a scalar field and an exponential potential whose
qualitative features have been studied previously. Particular attention is
focussed on those scalar-tensor theory cosmological models, which are shown to
be self-similar, that correspond to general relativistic models that play an
important r\^{o}le in describing the asymptotic behaviour of more general
models (e.g., those cosmological models that act as early-time and late-time
attractors).Comment: 22 pages, submitted to Phys Rev
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