17,222 research outputs found
Lessons from Recent Measurements of D-\bar D Mixing
An impressive progress in measurements of the D-\bar D mixing parameters has
been made in recent years. We explore the implications of these measurements to
models of new physics, especially in view of recent upper bounds on the amount
of CP violation. We update the constraints on non-renormalizable four-quark
operators. We show that the experiments are close to probing minimally flavor
violating models with large tan beta. The data challenge models with a scale of
order TeV where the flavor violation in the down sector is suppressed by
alignment and, in particular, certain classes of supersymmetric models and of
warped extra dimension models.Comment: 20 pages, 1 figure. Added references, minor corrections and
clarifications. Matches published versio
Can We Identify Lensed Gamma Ray Bursts?
A gravitationally lensed gamma-ray burst (GRB) would appear as multiple
bursts with identical light curves, separated in time and differing only by the
scaling of their amplitudes. However, noise may make them difficult to identify
as lensed images. Furthermore, faint, intrinsically similar, yet distinct light
curves may be falsely identified as lensing events. In this paper we develop
two statistical tests to distinguish noisy burst light curves. We use Fourier
analysis techniques to analyze the signals for both intrinsic variability and
variability due to noise. We are able to determine the noise level, and we
compare the bursts only at frequency channels that are signal dominated.
Utilizing these methods, we are able to make quantitative statements about
whether two bursts are distinct. We apply these statistics to scaled versions
of two subbursts of GRB 910503--- subbursts previously investigated by
Wambsganss (1993) using a different statistical test. We find that our methods
are able to distinguish these bursts at slightly smaller amplitudes than those
at which Wambsganss's method succeeds. We then apply our techniques to
``candidate" lensing events taken from the BATSE catalogue, and we find that
nearly all of them, except for the very shortest ones (durations \aproxlt 0.3
~s), are distinguishable. We therefore expect that a majority of bursts will
be disinguishable from one another.Comment: 28 pages, plain TeX (Figures Available as Post Script Files
Experimental marginal leakage around dental amalgams placed in artificial cavities
Experimental marginal leakage of high- and low-Cu amalgam restorations placed in acrylic teeth, where the cavities were untreated or painted with denatured collagen and/or a CaP slurry, was assessed after specimens were stored in a 1% NaCl solution for ten days and for one yr. All specimens stored for ten days showed severe marginal leakage. High- and low-Cu amalgam restorations placed in untreated acrylic teeth cavities formed seals after a storage period of one yr, indicating that these materials are able to form a seal without interacting with a natural tooth cavity interface. Cavities treated with denatured collagen also formed seals in the long-term group. It was apparent that, when the CaP slurry was used, generally more leakage resulted after the year's storage period than when amalgam restorations were placed in uncoated acrylic cavity surfaces or in those painted with denatured collagen.TS2016
Leptogenesis from Supersymmetry Breaking
We show that soft supersymmetry breaking terms involving the heavy sneutrinos
can lead to sneutrino-antisneutrino mixing and to new sources of CP violation,
which are present even if a single generation is considered. These terms are
naturally present in supersymmetric versions of leptogenesis scenarios, and
they induce indirect CP violation in the decays of the heavy sneutrinos,
eventually generating a baryon asymmetry. This new contribution can be
comparable to or even dominate over the asymmetry produced in traditional
leptogenesis scenarios.Comment: 4 pages; An improved discussion of the relevant numerical range of
the soft breaking terms (in agreement with hep-ph/0308031
Relating leptogenesis parameters to light neutrino masses
We obtain model independent relations among neutrino masses and leptogenesis
parameters. We find exact relations that involve the CP asymmetries
, the washout parameters and
, and the neutrino masses and , as well
as powerful inequalities that involve just and . We
prove that the Yukawa interactions of at least two of the heavy singlet
neutrinos are in the strong washout region ().Comment: 5 pages, 1 figur
Investigating diachronic trends in phonological inventories using BDPROTO
Here we present an expanded version of bdproto, a database comprising phonological inventory data from 257 ancient and reconstructed languages. These data were extracted from historical linguistic reconstructions and brought together into a single unified, normalized, accessible, and Unicode-compliant language resource. This dataset is publicly available and we aim to engage language scientists doing research on language change and language evolution. Furthermore, we identify a hitherto undiscussed temporal bias that complicates the simple comparison of ancient and reconstructed languages with present-day languages. Due to the sparsity of the data and the absence of statistical and computational methods that can adequately handle this bias, we instead directly target rates of change within and across families, thereby providing a case study to highlight bdproto’s research viability; using phylogenetic comparative methods and high-resolution language family trees, we investigate whether consonantal and vocalic systems differ in their rates of change over the last 10,000 years. In light of the compilation of bdproto and the findings of our case study, we discuss the challenges involved in comparing the sound systems of reconstructed languages with modern day languages
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UPC++ v1.0 Programmer’s Guide, Revision 2020.3.0
UPC++ is a C++11 library that provides Partitioned Global Address Space (PGAS) programming. It is designed for writing parallel programs that run efficiently and scale well on distributed-memory parallel computers. The PGAS model is single program, multiple-data (SPMD), with each separate constituent process having access to local memory as it would in C++. However, PGAS also provides access to a global address space, which is allocated in shared segments that are distributed over the processes. UPC++ provides numerous methods for accessing and using global memory. In UPC++, all operations that access remote memory are explicit, which encourages programmers to be aware of the cost of communication and data movement. Moreover, all remote-memory access operations are by default asynchronous, to enable programmers to write code that scales well even on hundreds of thousands of cores
On the Neutral Scalar Sector of the General R-parity Violating MSSM
Starting out from the most general, gauge invariant and renormalizable scalar
potential of the R-parity violating MSSM and performing a calculable rotation
to the scalar fields we arrive at a basis where the sneutrino VEVs are zero.
The advantage of our rotation is that, in addition, we obtain diagonal soft
supersymmetry breaking sneutrino masses and all potential parameters and VEVs
real, proving that the MSSM scalar potential does not exhibit spontaneous or
explicit CP-violation at tree level. The model has five CP-even and four CP-odd
physical neutral scalars, with at least one CP-even scalar lighter than M_Z. We
parametrise the neutral scalar sector in a way that resembles the
parametrisation of the R-parity conserving MSSM, analyze its mass spectrum, the
coupling to the gauge sector and the stability of the potential.Comment: 19 pages, minor changes, published version to appear in PL
The energy flux into a fluidized granular medium at a vibrating wall
We study the power input of a vibrating wall into a fluidized granular
medium, using event driven simulations of a model granular system. The system
consists of inelastic hard disks contained between a stationary and a vibrating
elastic wall, in the absence of gravity. Two scaling relations for the power
input are found, both involving the pressure. The transition between the two
occurs when waves generated at the moving wall can propagate across the system.
Choosing an appropriate waveform for the vibrating wall removes one of these
scalings and renders the second very simple.Comment: 5 pages, revtex, 7 postscript figure
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