128 research outputs found
New Ways to Soft Leptogenesis
Soft supersymmetry breaking terms involving heavy singlet sneutrinos provide
new sources of lepton number violation and of CP violation. In addition to the
CP violation in mixing, investigated previously, we find that `soft
leptogenesis' can be generated by CP violation in decay and in the interference
of mixing and decay. These additional ways to leptogenesis can be significant
for a singlet neutrino Majorana mass that is not much larger than the
supersymmetry breaking scale, . In contrast to CP violation
in mixing, for some of these new contributions the sneutrino oscillation rate
can be much faster than the decay rate, so that the bilinear scalar term need
not be smaller than its natural scale.Comment: 18 pages, 3 figure
Soft leptogenesis in the inverse seesaw model
We consider leptogenesis induced by soft supersymmetry breaking terms ("soft
leptogenesis"), in the context of the inverse seesaw mechanism. In this model
there are lepton number (L) conserving and L-violating soft
supersymmetry-breaking B-terms involving the singlet sneutrinos which, together
with the -- generically small-- L-violating parameter responsible of the
neutrino mass, give a small mass splitting between the four singlet sneutrino
states of a single generation. In combination with the trilinear soft
supersymmetry breaking terms they also provide new CP violating phases needed
to generate a lepton asymmetry in the singlet sneutrino decays. We obtain that
in this scenario the lepton asymmetry is proportional to the L-conserving soft
supersymmetry-breaking B-term, and it is not suppressed by the L-violating
parameters. Consequently we find that, as in the standard see-saw case, this
mechanism can lead to sucessful leptogenesis only for relatively small value of
the relevant soft bilinear coupling. The right-handed neutrino masses can be
sufficiently low to elude the gravitino problem. Also the corresponding Yukawa
couplings involving the lightest of the right-handed neutrinos are constrained
to be \sum |Y_{1k}|^2\lesssim 10^{-7} which generically implies that the
neutrino mass spectrum has to be strongly hierarchical.Comment: 28 pages, 1 figure; some references added; final version to appear in
JHE
Toward a High-Frequency Pulsed-Detonation Actuator
This paper describes the continued development of an actuator, energized by pulsed detonations, that provides a pulsed jet suitable for flow control in high-speed applications. A high-speed valve, capable of delivering a pulsed stream of reactants a mixture of H2 and air at rates of up to 1500 pulses per second, has been constructed. The reactants burn in a resonant tube and the products exit the tube as a pulsed jet. High frequency pressure transducers have been used to monitor the pressure fluctuations in the device at various reactant injection frequencies, including both resonant and off-resonant conditions. Pulsed detonations have been demonstrated in the lambda/4 mode of an 8 inch long tube at approx. 600 Hz. The pulsed jet at the exit of the device has been observed using shadowgraph and an infrared camera
Appraising the Effectiveness of a Simple Evaluational Approach to Problems of Retardation and Behavior in Childhood
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67035/2/10.1177_000992287201100921.pd
Carbon clusters near the crossover to fullerene stability
The thermodynamic stability of structural isomers of ,
, and , including
fullerenes, is studied using density functional and quantum Monte Carlo
methods. The energetic ordering of the different isomers depends sensitively on
the treatment of electron correlation. Fixed-node diffusion quantum Monte Carlo
calculations predict that a isomer is the smallest stable
graphitic fragment and that the smallest stable fullerenes are the
and clusters with and
symmetry, respectively. These results support proposals that a
solid could be synthesized by cluster deposition.Comment: 4 pages, includes 4 figures. For additional graphics, online paper
and related information see http://www.tcm.phy.cam.ac.uk/~prck
Trade openness, income levels, and economic growth: the case of developing countries, 1970–2009.
This paper attempts to investigate the extent to which trade openness has had an impact on the levels of income and rates of growth in a sample of 115 developing countries for the period 1970–2009. Additionally, to assess whether there is an income level threshold for a country to benefit from international trade, the sample is broken down into three mutually exclusive groups of countries: low-income, lower middle-income, and upper middleincome countries. The main novelty of the paper lies on the use, on the one hand, of a new and better trade openness measure and, on the other hand, of non-stationary heterogeneous panel cointegration techniques to cope with the problem of cross-sectional dependence. The results show a positive bidirectional relationship between trade openness and income level in the long run, thus suggesting that trade openness is both a cause and a consequence of the level of income. The results for the short run, that is, the link between openness growth and economic growth, go in the same direction
Phenomenology of the nMSSM from colliders to cosmology
Low energy supersymmetric models provide a solution to the hierarchy problem
and also have the necessary ingredients to solve two of the most outstanding
issues in cosmology: the origin of dark matter and baryonic matter. One of the
most attractive features of this framework is that the relevant physical
processes are related to interactions at the weak scale and therefore may be
tested in collider experiments in the near future. This is true for the Minimal
Supersymmetric Standard Model (MSSM) as well as for its extension with the
addition of one singlet chiral superfield, the so-called nMSSM. It has been
recently shown that within the nMSSM an elegant solution to both the problem of
baryogenesis and dark matter may be found, that relies mostly on the mixing of
the singlet sector with the Higgs sector of the theory. In this work we review
the nMSSM model constraints from cosmology and present the associated collider
phenomenology at the LHC and the ILC. We show that the ILC will efficiently
probe the neutralino, chargino and Higgs sectors, allowing to confront
cosmological observations with computations based on collider measurements. We
also investigate the prospects for a direct detection of dark matter and the
constraints imposed by the current bounds of the electron electric dipole
moment in this model.Comment: 44 pp, 10 figures; Fig.9 replaced; discussion on CP violation
extended and references added; few minor additions in text about details of
the cut
CcrZ is a pneumococcal spatiotemporal cell cycle regulator that interacts with FtsZ and controls DNA replication by modulating the activity of DnaA.
Most bacteria replicate and segregate their DNA concomitantly while growing, before cell division takes place. How bacteria synchronize these different cell cycle events to ensure faithful chromosome inheritance by daughter cells is poorly understood. Here, we identify Cell Cycle Regulator protein interacting with FtsZ (CcrZ) as a conserved and essential protein in pneumococci and related Firmicutes such as Bacillus subtilis and Staphylococcus aureus. CcrZ couples cell division with DNA replication by controlling the activity of the master initiator of DNA replication, DnaA. The absence of CcrZ causes mis-timed and reduced initiation of DNA replication, which subsequently results in aberrant cell division. We show that CcrZ from Streptococcus pneumoniae interacts directly with the cytoskeleton protein FtsZ, which places CcrZ in the middle of the newborn cell where the DnaA-bound origin is positioned. This work uncovers a mechanism for control of the bacterial cell cycle in which CcrZ controls DnaA activity to ensure that the chromosome is replicated at the right time during the cell cycle
Flavor changing Z-decays from scalar interactions at a Giga-Z Linear Collider
The flavor changing decay Z -> d_I \bar{d}_J is investigated with special
emphasis on the b \bar{s} final state. Various models for flavor violation are
considered: two Higgs doublet models (2HDM's), supersymmetry (SUSY) with flavor
violation in the up and down-type squark mass matrices and SUSY with flavor
violation mediated by R-parity-violating interaction. We find that, within the
SUSY scenarios for flavor violation, the branching ratio for the decay Z -> b
\bar{s} can reach 10^{-6} for large \tan\beta values, while the typical size
for this branching ratio in the 2HDM's considered is about two orders of
magnitudes smaller at best. Thus, flavor changing SUSY signatures in radiative
Z decays such as Z -> b \bar{s} may be accessible to future ``Z factories''
such as a Giga-Z version of the TESLA design.Comment: 27 pages, 15 figures, REVTeX4. A new section added and a few minor
corrections were made in the tex
Singularly Perturbed Monotone Systems and an Application to Double Phosphorylation Cycles
The theory of monotone dynamical systems has been found very useful in the
modeling of some gene, protein, and signaling networks. In monotone systems,
every net feedback loop is positive. On the other hand, negative feedback loops
are important features of many systems, since they are required for adaptation
and precision. This paper shows that, provided that these negative loops act at
a comparatively fast time scale, the main dynamical property of (strongly)
monotone systems, convergence to steady states, is still valid. An application
is worked out to a double-phosphorylation ``futile cycle'' motif which plays a
central role in eukaryotic cell signaling.Comment: 21 pages, 3 figures, corrected typos, references remove
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