65 research outputs found
Planck-Scale Physics and Neutrino Masses
We discuss gravitationally induced masses and mass splittings of Majorana,
Zeldovich-Konopinski-Mahmoud and Dirac neutrinos. Among other implications,
these effects can provide a solution of the solar neutrino puzzle. In
particular, we show how this may work in the 17 keV neutrino picture.Comment: 10 pages, IC/92/79, SISSA-83/92/EP, LMU-04/92 (the preprint number
has been corrected; no other changes
Sparticle Spectra and LHC Signatures for Large Volume String Compactifications
We study the supersymmetric particle spectra and LHC collider observables for
the large-volume string models with a fundamental scale of 10^{11} GeV that
arise in moduli-fixed string compactifications with branes and fluxes. The
presence of magnetic fluxes on the brane world volume, required for chirality,
perturb the soft terms away from those previously computed in the dilute-flux
limit. We use the difference in high-scale gauge couplings to estimate the
magnitude of this perturbation and study the potential effects of the magnetic
fluxes by generating many random spectra with the soft terms perturbed around
the dilute flux limit. Even with a 40% variation in the high-scale soft terms
the low-energy spectra take a clear and predictive form. The resulting spectra
are broadly similar to those arising on the SPS1a slope, but more degenerate.
In their minimal version the models predict the ratios of gaugino masses to be
M_1 : M_2 : M_3=(1.5 - 2) : 2 : 6, different to both mSUGRA and mirage
mediation. Among the scalars, the squarks tend to be lighter and the sleptons
heavier than for comparable mSUGRA models. We generate 10 fb^{-1} of sample LHC
data for the random spectra in order to study the range of collider
phenomenology that can occur. We perform a detailed mass reconstruction on one
example large-volume string model spectrum. 100 fb^{-1} of integrated
luminosity is sufficient to discriminate the model from mSUGRA and aspects of
the sparticle spectrum can be accurately reconstructed.Comment: 42 pages, 21 figures. Added references and discussion for section 3.
Slight changes in the tex
New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation
(abridged) The heating mechanism at high densities during M dwarf flares is
poorly understood. Spectra of M dwarf flares in the optical and
near-ultraviolet wavelength regimes have revealed three continuum components
during the impulsive phase: 1) an energetically dominant blackbody component
with a color temperature of T 10,000 K in the blue-optical, 2) a smaller
amount of Balmer continuum emission in the near-ultraviolet at lambda 3646
Angstroms and 3) an apparent pseudo-continuum of blended high-order Balmer
lines. These properties are not reproduced by models that employ a typical
"solar-type" flare heating level in nonthermal electrons, and therefore our
understanding of these spectra is limited to a phenomenological interpretation.
We present a new 1D radiative-hydrodynamic model of an M dwarf flare from
precipitating nonthermal electrons with a large energy flux of erg
cm s. The simulation produces bright continuum emission from a
dense, hot chromospheric condensation. For the first time, the observed color
temperature and Balmer jump ratio are produced self-consistently in a
radiative-hydrodynamic flare model. We find that a T 10,000 K
blackbody-like continuum component and a small Balmer jump ratio result from
optically thick Balmer and Paschen recombination radiation, and thus the
properties of the flux spectrum are caused by blue light escaping over a larger
physical depth range compared to red and near-ultraviolet light. To model the
near-ultraviolet pseudo-continuum previously attributed to overlapping Balmer
lines, we include the extra Balmer continuum opacity from Landau-Zener
transitions that result from merged, high order energy levels of hydrogen in a
dense, partially ionized atmosphere. This reveals a new diagnostic of ambient
charge density in the densest regions of the atmosphere that are heated during
dMe and solar flares.Comment: 50 pages, 2 tables, 13 figures. Accepted for publication in the Solar
Physics Topical Issue, "Solar and Stellar Flares". Version 2 (June 22, 2015):
updated to include comments by Guest Editor. The final publication is
available at Springer via http://dx.doi.org/10.1007/s11207-015-0708-
Baseline characteristics of patients enrolled in the Exenatide Study of Cardiovascular Event Lowering (EXSCEL)
Background EXSCEL is a randomized, double-blind, placebo-controlled trial examining the effect of exenatide once-weekly (EQW) versus placebo on time to the primary composite outcome (cardiovascular death, nonfatal myocardial infarction or nonfatal stroke) in patients with type 2 diabetes mellitus (DM) and a wide range of cardiovascular (CV) risk. Methods Patients were enrolled at 688 sites in 35 countries. We describe their baseline characteristics according to prior CV event status and compare patients with those enrolled in prior glucagon-like peptide-1 receptor agonist (GLP-1RA) outcomes trials. Results Of a total of 14,752 participants randomized between June 2010 and September 2015, 6,788 (46.0%) patients were enrolled in Europe; 3,708 (25.1%), North America; 2,727 (18.5%), Latin America; and 1,529 (10.4%), Asia Pacific. Overall, 73% had at least one prior CV event (70% coronary artery disease, 24% peripheral arterial disease, 22% cerebrovascular disease). The median (IQR) age was 63 years (56, 69), 38% were female, median baseline HbA1c was 8.0% (7.3, 8.9) and 16% had a prior history of heart failure. Those without a prior CV event were younger with a shorter duration of diabetes and better renal function than those with at least one prior CV event. Compared with prior GLP-1RA trials, EXSCEL has a larger percentage of patients without a prior CV event and a notable percentage who were taking a dipeptidyl peptidase-4 inhibitor at baseline (15%). Conclusions EXSCEL is one of the largest global GLP-1RA trials, evaluating the safety and efficacy of EQW with a broad patient population that may extend generalizability compared to prior GLP-1RA trials (ClinicalTrials.gov number, NCT01144338)
Cold Plus Hot Dark Matter Cosmology in the Light of Solar and Atmospheric Neutrino Oscillations
We explore the implications of possible neutrino oscillations, as indicated
by the solar and atmospheric neutrino experiments, for the cold plus hot dark
matter scenario of large scale structure formation. We find that there are
essentially three distinct schemes that can accommodate the oscillation data
and which also allow for dark matter neutrinos. These include (i) three nearly
degenerate (in mass) neutrinos, (ii) non-degenerate masses with in
the eV range, and (iii) nearly degenerate pair (in the eV
range), with the additional possibility that the electron neutrino is
cosmologically significant. The last two schemes invoke a `sterile' neutrino
which is light (< or ~ eV). We discuss the implications of these schemes for
and oscillation, and find
that scheme (ii) in particular, predicts them to be in the observable range. As
far as structure formation is concerned, we compare the one neutrino flavor
case with a variety of other possibilities, including two and three degenerate
neutrino flavors. We show, both analytically and numerically, the effects of
these neutrino mass scenarios on the amplitude of cosmological density
fluctuations. With a Hubble constant of 50 km s Mpc, a spectral
index of unity, and , the two and three flavor
scenarios fit the observational data marginally better than the single flavor
scheme. However, taking account of the uncertainties in these parameters, we
show that it is premature to pick a clear winner.Comment: 1 LaTEX file plus 1 uuencoded Z-compressed tar file with 3 postscript
figure
UBVRI Light curves of 44 Type Ia supernovae
We present UBVRI photometry of 44 Type la supernovae (SNe la) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SNe la to date, nearly doubling the number of well-observed, nearby SNe la with published multicolor CCD light curves. The large sample of [U-band photometry is a unique addition, with important connections to SNe la observed at high redshift. The decline rate of SN la U-band light curves correlates well with the decline rate in other bands, as does the U - B color at maximum light. However, the U-band peak magnitudes show an increased dispersion relative to other bands even after accounting for extinction and decline rate, amounting to an additional ∼40% intrinsic scatter compared to the B band
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