1,719 research outputs found
Probing the two-scale-factor universality hypothesis by exact rotation symmetry-breaking mechanism
We probe the two-scale factor universality hypothesis by evaluating, firstly
explicitly and analytically at the one-loop order, the loop quantum corrections
to the amplitude ratios for O() scalar field theories with
rotation symmetry-breaking in three distinct and independent methods in which
the rotation symmetry-breaking mechanism is treated exactly. We show that the
rotation symmetry-breaking amplitude ratios turn out to be identical in the
three methods and equal to their respective rotation symmetry-breaking ones,
although the amplitudes themselves, in general, depend on the method employed
and on the rotation symmetry-breaking parameter. At the end, we show that all
these results can be generalized, through an inductive process based on a
general theorem emerging from the exact calculation, to any loop level and
physically interpreted based on symmetry ideas.Comment: 17 pages, 3 figure
Caracterizacao dos frutos de goiabeira e selecao de cultivares na regiao do Submedio Sao Francisco.
O estudo visou a caracterizar frutos de goiabeira e selecionar cultivares produzidas na regiao do Submedio Sao Francisco. Os frutos, colhidos na maturidade fisiologica, foram provenientes da estacao Experimental de Bebedouro, pertencente a Embrapa Semi-Arido e avaliados em delineamento experimental inteiramente casualizado com quatro repeticoes. Os tratamentos compreenderam genotipos de polpa branca (Alabama Safed, Lucknow 49, Banahas, White Selection of Florida e Selecao IPA B 38.1) e vermelha (Paluma, Patillo 2.1, Surubim, Red Selection of Florida e Selecao IPA B 14.3). Avaliaram-se: massa, diametro longitudinal (DL), diametro transversal (DT), relacao DL/DT, espessura da casca, espessura da polpa, solidos soluveis totais (SST), acidez total titulavel (ATT), relacao SST/ATT, pH, acucares soluveis totais (AST) e vitamina C. Os genotipos de polpa branca, exceto Selecao IPA B 38.1, tiveram maiores massas (acima de 145,0g). As menores relacoes DL/DT foram observadas e Banahas (0,98) e Lucknow 49 (1,00), caracterizando frutos redondos. Estas cultivares tiveram tambem maior espessura da polpa. Os maiores valores de SST foram observados em Paluma (10,4 oBrix) e Lucknow 49 (10,9 oBrix). A ATT foi baixa na maioria dos genotipos, exceto Surubim e Selecao IPA B 14,3, e o pH variou de 3,72 a 4,22. Em geral, os genotipos de polpa branca tiveram os maiores teores de AST (5 a 7%) e vitamina C, atingindo 200 mg de acido ascorbico/100g
Avaliação da pinta-preta em progênies de mamoeiro no Estado do Ceará.
O mamoeiro é uma fruteira tropical de grande importância socioeconômica no Brasil e no mundo e o estado do Ceará destaca-se como o terceiro produtor brasileiro de mamão. A ocorrência de doenças é um dos fatores que contribuem para essa produtividade, por causarem perdas severas na cultura (VENTURA et al., 2003)
Formation of a spiral galaxy in a major merger
We use numerical simulations to examine the structure of merger remnants
resulting from collisions of gas-rich spiral galaxies. When the gas fraction of
the progenitors is small, the remnants structurally and kinematically resemble
elliptical galaxies, in agreement with earlier work. However, if the progenitor
disks are gas-dominated, new types of outcomes are possible. In fact, we show
that a prominent disk may survive in certain cases. To illustrate this
scenario, we analyze an extreme example with progenitor galaxies consisting of
dark matter halos, pure gas disks, and no bulges, as might be appropriate for
mergers at high redshifts. While rapid star formation triggered by tidal
torques during the merger forms a central, rotating bulge in the remnant, not
all the gas is consumed in the burst. The remaining gas cools very quickly and
settles into an extended star-forming disk, yielding an object similar to a
spiral galaxy, and not an early type galaxy. This is contrary to the usual view
that major mergers invariably destroy disks. The morphological evolution of
galaxies can therefore be more complicated than often assumed, and in
particular, theoretical constraints based on the fragility of spiral disks need
to be reevaluated.Comment: submitted to ApJL, 4 figure
Gemini and Chandra observations of Abell 586, a relaxed strong-lensing cluster
We analyze the mass content of the massive strong-lensing cluster Abell 586
(). We use optical data (imaging and spectroscopy) obtained with the
Gemini Multi-Object Spectrograph (GMOS) mounted on the 8-m Gemini-North
telescope, together with publicly available X-ray data taken with the
\textit{Chandra} space telescope. Employing different techniques -- velocity
distribution of galaxies, weak gravitational lensing, and X-ray spatially
resolved spectroscopy -- we derive mass and velocity dispersion estimates from
each of them. All estimates agree well with each other, within a 68% confidence
level, indicating a velocity dispersion of 1000 -- 1250 \kms. The projected
mass distributions obtained through weak-lensing and X-ray emission are
strikingly similar, having nearly circular geometry. We suggest that Abell 586
is probably a truly relaxed cluster, whose last major merger occurred more than
Gyr agoComment: ApJ accepted, 20 pages, 11 figures; Figure 1 fixe
Radial Temperature Profiles of X-Ray--Emitting Gas Within Clusters of Galaxies
Previous analyses of ASCA data of clusters of galaxies have found conflicting
results regarding the slope of the temperature profile of the hot X-ray gas
within clusters, mainly because of the large, energy-dependent point spread
function (PSF) of the ASCA mirrors. We present a summary of all ASCA-determined
cluster temperature profiles found in the literature, and find a discrepancy in
the radial temperature trend of clusters based on which PSF-correction routine
is used. This uncertainty in the cluster temperature profile in turn can lead
to large uncertainties in the amount of dark matter in clusters. In this study,
we have used ROSAT PSPC data to obtain independent relative temperature
profiles for 26 clusters, most of which have had their temperature profiles
determined by ASCA. Our aim is not to measure the actual temperature values of
the clusters, but to use X-ray color profiles to search for a hardening or
softening of the spectra with radius for comparison to ASCA-derived profiles.
The radial color profiles indicate that outside of the cooling flow region, the
temperature profiles of clusters are in general constant. Within 35% of the
virial radius, we find a temperature drop of 20% at 10 keV and 12% at 5 keV can
be ruled out at the 99% confidence level. A subsample of non-cooling flow
clusters shows that the condition of isothermality applies at very small radii
too, although cooling gas complicates this determination in the cooling flow
subsample. The colors predicted from the temperature profiles of a series of
hydrodynamical cluster simulations match the data very well, although they
cannot be used to discriminate among different cosmologies. An additional
result is that the color profiles show evidence for a central peak in
metallicity in low temperature clusters.Comment: 39 pages, 15 embedded Postscript figures, uses aaspp4.sty, accepted
for publication in Astrophysical Journa
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