24,745 research outputs found
An Updated Numerical Analysis of eV Seesaw with Four Generations
We consider the so-called "eV seesaw" scenario, with right-handed Majorana
mass at eV order, extended to four lepton generations. The fourth
generation gives a heavy pseudo-Dirac neutral lepton, which largely decouples
from other generations and is relatively stable. The framework naturally gives
3 active and 3 sterile neutrinos. We update a previous numerical analysis of a
3+3 study of the LSND anomaly, taking into account the more recent results from
the MiniBooNE experiment. In particular, we study the implications for the
third mixing angle , as well as CP violation. We
find that current data do not seriously constrain more than one sterile
neutrinos.Comment: References updated, and a Note Adde
Spectroscopic Confirmation of a Protocluster at z=3.786
We present new observations of the field containing the z=3.786 protocluster,
PC217.96+32.3. We confirm that it is one of the largest and most overdense
high-redshift structures known. Such structures are rare even in the largest
cosmological simulations. We used the Mayall/MOSAIC1.1 imaging camera to image
a 1.2x0.6 deg area (~150x75 comoving Mpc) surrounding the protocluster's core
and discovered 165 candidate Lyman Alpha emitting galaxies (LAEs) and 788
candidate Lyman Break galaxies (LBGs). There are at least 2 overdense regions
traced by the LAEs, the largest of which shows an areal overdensity in its core
(i.e., within a radius of 2.5 comoving Mpc) of 14+/-7 relative to the average
LAE spatial density in the imaged field. Further, the average LAE spatial
density in the imaged field is twice that derived by other field LAE surveys.
Spectroscopy with Keck/DEIMOS yielded redshifts for 164 galaxies (79 LAEs and
85 LBGs); 65 lie at a redshift of 3.785+/-0.010. The velocity dispersion of
galaxies near the core is 350+/-40 km/s, a value robust to selection effects.
The overdensities are likely to collapse into systems with present-day masses
of >10^{15} solar masses and >6x10^{14} solar masses. The low velocity
dispersion may suggest a dynamically young protocluster. We find a weak trend
between narrow-band (Lyman Alpha) luminosity and environmental density: the
Lyman Alpha luminosity is enhanced on average by 1.35X within the protocluster
core. There is no evidence that the Lyman Alpha equivalent width depends on
environment. These suggest that star-formation and/or AGN activity is enhanced
in the higher density regions of the structure. PC217.96+32.3 is a Coma cluster
analog, witnessed in the process of formation.Comment: Accepted for publication in the Astrophysical Journal (March 27,
2016
Ultrasound attenuation and a P-B-T phase diagram of superfluid 3He in 98% aerogel
Longitudinal sound attenuation measurements in superfluid 3He in 98% aerogel
were conducted at pressures between 14 and 33 bar and in magnetic fields up to
4.44 kG. The temperature dependence of the ultrasound attenuation in the A-like
phase was determined for the entire superfluid region exploiting the field
induced meta-stable A-like phase at the highest field. In the lower field, the
A-B transition in aerogel was identified by a smooth jump in attenuation on
both cooling and warming. Based on the transitions observed on warming, a phase
diagram as a function of pressure (P), temperature (T) and magnetic field (B)
is constructed. We find that the A-B phase boundary in aerogel recedes in a
drastically different manner than in bulk in response to an increasing magnetic
field. The implications of the observed phase diagram are discussed.Comment: 9 pages, 13 figures, accepted to PR
Enhanced Tissue Integration During Cartilage RepairIn VitroCan Be Achieved by Inhibiting Chondrocyte Death at the Wound Edge
Objective: Experimental wounding of articular cartilage results in cell death at the lesion edge. The objective of this study was to investigate whether inhibition of this cell death results in enhanced integrative cartilage repair. Methods: Bovine articular cartilage discs (6mm) were incubated in media containing inhibitors of necrosis (Necrostatin-1, Nec-1) or apoptosis (Z-VAD-FMK, ZVF) before cutting a 3mm inner core. This core was left in situ to create disc/ring composites, cultured for up to 6 weeks with the inhibitors, and analyzed for cell death, sulfated glycosaminoglycan release, and tissue integration. Results: Creating the disc/ring composites resulted in a significant increase in necrosis. ZVF significantly reduced necrosis and apoptosis at the wound edge. Nec-1 reduced necrosis. Both inhibitors reduced the level of wound-induced sulfated glycosaminoglycan loss. Toluidine blue staining and electron microscopy of cartilage revealed significant integration of the wound edges in disc/ring composites treated with ZVF. Nec-1 improved integration, but to a lesser extent. Push-out testing revealed that ZVF increased adhesive strength compared to control composites. Conclusions: This study shows that treatment of articular cartilage with cell death inhibitors during wound repair increases the number of viable cells at the wound edge, prevents matrix loss, and results in a significant improvement in cartilage-cartilage integration
Non-renormalization of next-to-extremal correlators in N=4 SYM and the AdS/CFT correspondence
We show that next-to-extremal correlators of chiral primary operators in N=4
SYM theory do not receive quantum corrections to first order in perturbation
theory. Furthermore we consider next-to-extremal correlators within AdS
supergravity. Here the exchange diagrams contributing to these correlators
yield results of the same free-field form as obtained within field theory. This
suggests that quantum corrections vanish at strong coupling as well.Comment: 21 pages, LaTex, 9 eps figures, typos corrected and references adde
The Diversity of Diffuse Ly Nebulae around Star-Forming Galaxies at High Redshift
We report the detection of diffuse Ly emission, or Ly halos
(LAHs), around star-forming galaxies at and in the NOAO
Deep Wide-Field Survey Bo\"otes field. Our samples consist of a total of
1400 galaxies, within two separate regions containing spectroscopically
confirmed galaxy overdensities. They provide a unique opportunity to
investigate how the LAH characteristics vary with host galaxy large-scale
environment and physical properties. We stack Ly images of different
samples defined by these properties and measure their median LAH sizes by
decomposing the stacked Ly radial profile into a compact galaxy-like
and an extended halo-like component. We find that the exponential scale-length
of LAHs depends on UV continuum and Ly luminosities, but not on
Ly equivalent widths or galaxy overdensity parameters. The full
samples, which are dominated by low UV-continuum luminosity Ly emitters
(), exhibit LAH sizes of 5kpc. However, the
most UV- or Ly-luminous galaxies have more extended halos with
scale-lengths of 7kpc. The stacked Ly radial profiles decline
more steeply than recent theoretical predictions that include the contributions
from gravitational cooling of infalling gas and from low-level star formation
in satellites. On the other hand, the LAH extent matches what one would expect
for photons produced in the galaxy and then resonantly scattered by gas in an
outflowing envelope. The observed trends of LAH sizes with host galaxy
properties suggest that the physical conditions of the circumgalactic medium
(covering fraction, HI column density, and outflow velocity) change with halo
mass and/or star-formation rates.Comment: published in ApJ, minor proof corrections applie
Galaxy Cluster Correlation Function to z ~ 1.5 in the IRAC Shallow Cluster Survey
We present the galaxy cluster autocorrelation function of 277 galaxy cluster
candidates with 0.25 \le z \le 1.5 in a 7 deg^2 area of the IRAC Shallow
Cluster Survey. We find strong clustering throughout our galaxy cluster sample,
as expected for these massive structures. Specifically, at = 0.5 we find a
correlation length of r_0 = 17.40^{+3.98}_{-3.10} h^-1 Mpc, in excellent
agreement with the Las Campanas Distant Cluster Survey, the only other
non-local measurement. At higher redshift, = 1, we find that strong
clustering persists, with a correlation length of r_0=19.14^{+5.65}_{-4.56}
h^-1 Mpc. A comparison with high resolution cosmological simulations indicates
these are clusters with halo masses of \sim 10^{14} Msun, a result supported by
estimates of dynamical mass for a subset of the sample. In a stable clustering
picture, these clusters will evolve into massive (10^{15} Msun) clusters by the
present day.Comment: 4 pages, 4 figures, 1 table. ApJ Letters, in pres
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