1,531 research outputs found
Dynamical stabilization of matter-wave solitons revisited
We consider dynamical stabilization of Bose-Einstein condensates (BEC) by
time-dependent modulation of the scattering length. The problem has been
studied before by several methods: Gaussian variational approximation, the
method of moments, method of modulated Townes soliton, and the direct averaging
of the Gross-Pitaevskii (GP) equation. We summarize these methods and find that
the numerically obtained stabilized solution has different configuration than
that assumed by the theoretical methods (in particular a phase of the
wavefunction is not quadratic with ). We show that there is presently no
clear evidence for stabilization in a strict sense, because in the numerical
experiments only metastable (slowly decaying) solutions have been obtained. In
other words, neither numerical nor mathematical evidence for a new kind of
soliton solutions have been revealed so far. The existence of the metastable
solutions is nevertheless an interesting and complicated phenomenon on its own.
We try some non-Gaussian variational trial functions to obtain better
predictions for the critical nonlinearity for metastabilization but
other dynamical properties of the solutions remain difficult to predict
The Grism Lens-Amplified Survey from Space (GLASS). IX. The dual origin of low-mass cluster galaxies as revealed by new structural analyses
Using deep Hubble Frontier Fields imaging and slitless spectroscopy from the
Grism Lens-Amplified Survey from Space, we analyze 2200 cluster and 1748 field
galaxies at to determine the impact of environment on galaxy
size and structure at , an unprecedented limit at these
redshifts. Based on simple assumptions--we find no significant
differences in half-light radii () between equal-mass cluster or field
systems. More complex analyses-)-reveal local density
) to induce only a ( confidence) reduction in
beyond what can be accounted for by color, Sersic index (), and
redshift () effects.Almost any size difference between galaxies in high- and
low-density regions is thus attributable to their different distributions in
properties other than environment. Indeed, we find a clear color-
correlation in low-mass passive cluster galaxies () such
that bluer systems have larger radii, with the bluest having sizes consistent
with equal-mass star-forming galaxies. We take this as evidence that
large- low-mass passive cluster galaxies are recently acquired systems
that have been environmentally quenched without significant structural
transformation (e.g., by ram pressure stripping or starvation).Conversely,
of small- low-mass passive cluster galaxies appear to have been
in place since . Given the consistency of the small- galaxies'
stellar surface densities (and even colors) with those of systems more than ten
times as massive, our findings suggest that clusters mark places where galaxy
evolution is accelerated for an ancient base population spanning most masses,
with late-time additions quenched by environment-specific mechanisms are mainly
restricted to the lowest masses.Comment: The accepted version. The catalog is available through the GLASS web
page (http://glass.astro.ucla.edu), or
https://www.astr.tohoku.ac.jp/~mtakahiro/Publication/Morishita17
Suggestions for a way forward to further evaluate ageing error for Southern Hemisphere minke whales.
Paper SC/59/O8 provides a very helpful perspective and suggestions to help clarify the use of Antarctic minke whale age data in the commercial and research permit periods. On the basis of the paper, some areas for further work suggest themselves and these are outlined below. We recognise that these involve, in some cases, quite substantial additional work but believe that this will assist considerably in addressing the issues raised inter alia at the JARPA review meeting as well as during past IA sub-committee meetings and allow the valuable analyses involving both commercial and scientific permit data to be undertaken. The second experiment is designed to confirm the proposal in SC/59/O8 to limit analyses to using only data for animals aged six years and over
Spectroscopic confirmation of an ultra-faint galaxy at the epoch of reionization
Within one billion years of the Big Bang, intergalactic hydrogen was ionized
by sources emitting ultraviolet and higher energy photons. This was the final
phenomenon to globally affect all the baryons (visible matter) in the Universe.
It is referred to as cosmic reionization and is an integral component of
cosmology. It is broadly expected that intrinsically faint galaxies were the
primary ionizing sources due to their abundance in this epoch. However, at the
highest redshifts (; lookback time 13.1 Gyr), all galaxies with
spectroscopic confirmations to date are intrinsically bright and, therefore,
not necessarily representative of the general population. Here, we report the
unequivocal spectroscopic detection of a low luminosity galaxy at . We
detected the Lyman- emission line at {\AA} in two separate
observations with MOSFIRE on the Keck I Telescope and independently with the
Hubble Space Telescope's slit-less grism spectrograph, implying a source
redshift of . The galaxy is gravitationally magnified by
the massive galaxy cluster MACS J1423.8+2404 (), with an estimated
intrinsic luminosity of mag and a stellar mass of
solar masses. Both are an order of
magnitude lower than the four other Lyman- emitters currently known at
, making it probably the most distant representative source of
reionization found to date
Detection of Lyman-Alpha Emission From a Triple Imaged z=6.85 Galaxy Behind MACS J2129.4-0741
We report the detection of Ly emission at \AA{} in the
Keck/DEIMOS and \HST WFC3 G102 grism data from a triply-imaged galaxy at
behind galaxy cluster MACS J2129.40741. Combining the
emission line wavelength with broadband photometry, line ratio upper limits,
and lens modeling, we rule out the scenario that this emission line is \oii at
. After accounting for magnification, we calculate the weighted average
of the intrinsic Ly luminosity to be
and Ly equivalent
width to be \AA{}. Its intrinsic UV absolute magnitude at 1600\AA{} is
mag and stellar mass , making
it one of the faintest (intrinsic ) galaxies with
Ly detection at to date. Its stellar mass is in the typical
range for the galaxies thought to dominate the reionization photon budget at
; the inferred Ly escape fraction is high (\%),
which could be common for sub- galaxies with Ly
emission. This galaxy offers a glimpse of the galaxy population that is thought
to drive reionization, and it shows that gravitational lensing is an important
avenue to probe the sub- galaxy population.Comment: Accepted by ApJ Letter
Quark spin coupling in baryons - revisited
A direct connection can be made between mixing angles in negative parity
baryons and the spin coupling of constituent quarks. The mixing angles do not
depend on spectral data. These angles are recalculated for gluon exchange and
pion exchange between quarks. For pion exchange the results of Glozman and
Riska are corrected. The experimental data on mixing are very similar to those
derived from gluon exchange but substantially different from the values
obtained for pion exchange.Comment: 10 pages, RevTex; a sign error is corrected, spin-orbit results are
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