5,146 research outputs found
Warped Supersymmetric Unification with Non-Unified Superparticle Spectrum
We present a new supersymmetric extension of the standard model. The model is
constructed in warped space, with a unified bulk symmetry broken by boundary
conditions on both the Planck and TeV branes. In the supersymmetric limit, the
massless spectrum contains exotic colored particles along with the particle
content of the minimal supersymmetric standard model (MSSM). Nevertheless, the
model still reproduces the MSSM prediction for gauge coupling unification and
does not suffer from a proton decay problem. The exotic states acquire masses
from supersymmetry breaking, making the model completely viable, but there is
still the possibility that these states will be detected at the LHC. The
lightest of these states is most likely A_5^XY, the fifth component of the
gauge field associated with the broken unified symmetry. Because supersymmetry
is broken on the SU(5)-violating TeV brane, the gaugino masses generated at the
TeV scale are completely independent of one another. We explore some of the
unusual features that the superparticle spectrum might have as a consequence.Comment: 21 pages, Latex, version to appear in Phys. Rev.
Teaching versus Research: An Imbalance of Importance?
This article features two essays presenting the major argumentative positions advanced by teams Robert E. Pruett and James E. Sayer and Norbert H. Mills and David E. Tucker, regarding the topic: Resolved: that teaching and research are mutually-exclusive activities. Pruett and Sayer upheld the affirmative position on the resolution, while Mills and Tucker upheld the negative. In the traditional sense, it is easy to claim that the function of a professor is twofold: to be an effective and creative teacher and, at the same time, be able to accumulate and disseminate knowledge through research. Regardless of what is said, teaching has become subservient to research and, while the responsibility of faculty members is to remain current in their fields, research is a separate activity that does not necessarily make one a better teacher and certainly is exclusive from the teaching function. N. Mills and D. Tucker contend that there is no constituency because teaching has been devalued and separated from research
Singlet-Doublet Dark Matter
In light of recent data from direct detection experiments and the Large
Hadron Collider, we explore models of dark matter in which an SU(2) doublet is
mixed with a Standard Model singlet. We impose a thermal history. If the new
particles are fermions, this model is already constrained due to null results
from XENON100. We comment on remaining regions of parameter space and assess
prospects for future discovery. We do the same for the model where the new
particles are scalars, which at present is less constrained. Much of the
remaining parameter space for both models will be probed by the next generation
of direct detection experiments. For the fermion model, DeepCore may also play
an important role.Comment: 32 pages, 10 figures; v2 minor changes, references adde
The improved prognosis of hypoplastic left heart:A Population-Based Register Study of 343 Cases in England and Wales
Background: Hypoplastic Left Heart Syndrome (HLHS) is a severe congenital heart defect (CHD) characterised by the underdevelopment of the left side of the heart with varying levels of hypoplasia of the left atrium, mitral valve, left ventricle, aortic valve and aortic arch. In the UK, age 12 survival for cases born between 1991 and 1993 was 21%. UK survival estimates corresponding to cases born between 2000 and 2015 were improved at 56%, but survival was examined up to age five only. Contemporary long-term survival estimates play a crucial role in counselling parents following diagnosis. The aim of this study was to report survival estimates up to age 15 for children born with HLHS or hypoplastic left ventricle with additional CHD in England and Wales between 1998 and 2012. Methods: Cases of HLHS notified to four congenital anomaly registers in England and Wales during 1998–2012, matched to Office for National Statistics mortality information, were included. Kaplan-Meier survival estimates to age 15 were reported. Cox regression models were fitted to examine risk factors for mortality. Results: There were 244 cases of HLHS and 99 cases of hypoplastic left ventricle co-occurring with other CHD, with traced survival status. Kaplan-Meier survival estimates for HLHS were 84.4% at age 1 week, 76.2% at 1 month, 63.5% at age 1 year, 58.6% at age 5 years, 54.6% at age 10 years, and 32.6% to age 15 years. The Kaplan-Meier survival estimates for cases of hypoplastic left ventricle co-occurring with additional CHD were 90.9% at age 1 week, 84.9% at 1 month, 73.7% at age 1 year, 67.7% to age 5 years, 59.2% to age 10 years, and 40.3% to age 15 years. Preterm birth (p = 0.007), low birth weight (p = 0.005), and female sex (p = 0.01) were associated with mortality. Conclusions: We have shown that prognosis associated with HLHS in the twenty first century exceeds that of many previous population-based studies, likely due to improvements in intensive care technologies and advances in surgical techniques over the last few decades
Spectral signatures of photosynthesis II: coevolution with other stars and the atmosphere on extrasolar worlds
As photosynthesis on Earth produces the primary signatures of life that can
be detected astronomically at the global scale, a strong focus of the search
for extrasolar life will be photosynthesis, particularly photosynthesis that
has evolved with a different parent star. We take planetary atmospheric
compositions simulated by Segura, et al. (2003, 2005) for Earth-like planets
around observed F2V and K2V stars, modeled M1V and M5V stars, and around the
active M4.5V star AD Leo; our scenarios use Earth's atmospheric composition as
well as very low O2 content in case anoxygenic photosynthesis dominates. We
calculate the incident spectral photon flux densities at the surface of the
planet and under water. We identify bands of available photosynthetically
relevant radiation and find that photosynthetic pigments on planets around F2V
stars may peak in absorbance in the blue, K2V in the red-orange, and M stars in
the NIR, in bands at 0.93-1.1 microns, 1.1-1.4 microns, 1.5-1.8 microns, and
1.8-2.5 microns. In addition, we calculate wavelength restrictions for
underwater organisms and depths of water at which they would be protected from
UV flares in the early life of M stars. We estimate the potential productivity
for both surface and underwater photosynthesis, for both oxygenic and
anoxygenic photosynthesis, and for hypothetical photosynthesis in which longer
wavelength, multi-photosystem series are used.Comment: 59 pages, 4 figures, 4 tables, forthcoming in Astrobiology ~March
200
Improving Human Health by Increasing Access to Natural Areas: Linking Research to Action at Scale
Report of the 2014 Berkley Workshop
Held at the Wingspread Conference Center, Johnson Foundation, Racine, Wisconsin - June 201
Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations
Our Galaxy hosts the annihilation of a few low-energy
positrons every second. Radioactive isotopes capable of supplying such
positrons are synthesised in stars, stellar remnants, and supernovae. For
decades, however, there has been no positive identification of a main stellar
positron source leading to suggestions that many positrons originate from
exotic sources like the Galaxy's central super-massive black hole or dark
matter annihilation. %, but such sources would not explain the
recently-detected positron signal from the extended Galactic disk. Here we show
that a single type of transient source, deriving from stellar populations of
age 3-6 Gyr and yielding ~0.03 of the positron emitter Ti, can
simultaneously explain the strength and morphology of the Galactic positron
annihilation signal and the solar system abundance of the Ti decay
product Ca. This transient is likely the merger of two low-mass white
dwarfs, observed in external galaxies as the sub-luminous, thermonuclear
supernova known as SN1991bg-like.Comment: 28 pages main text with 4 figures in preprint style; 26 pages of
Supplementary Informatio
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