2,021 research outputs found
Highest weight representations and Kac determinants for a class of conformal Galilei algebras with central extension
We investigate the representations of a class of conformal Galilei algebras
in one spatial dimension with central extension. This is done by explicitly
constructing all singular vectors within the Verma modules, proving their
completeness and then deducing irreducibility of the associated highest weight
quotient modules. A resulting classification of infinite dimensional
irreducible modules is presented. It is also shown that a formula for the Kac
determinant is deduced from our construction of singular vectors. Thus we prove
a conjecture of Dobrev, Doebner and Mrugalla for the case of the Schrodinger
algebra.Comment: 24 page
Dark matter in the classically conformal B-L model
When the classically conformal invariance is imposed on the minimal gauged
B-L extended Standard Model (SM), the B-L gauge symmetry is broken by the
Coleman-Weinberg mechanism naturally at the TeV scale. Introducing a new Z_2
parity in the model, we investigate phenomenology of a right-handed neutrino
dark matter whose stability is ensured by the parity. We find that the relic
abundance of the dark matter particle can be consistent with the observations
through annihilation processes enhanced by resonances of either the SM Higgs
boson, the B-L Higgs boson or the B-L gauge boson (Z' boson). Therefore, the
dark matter mass is close to half of one of these boson masses. Due to the
classically conformal invariance and the B-L gauge symmetry breaking via the
Coleman-Weinberg mechanism, Higgs boson masses, Z' boson mass and the dark
matter mass are all related, and we identify the mass region to be consistent
with experimental results. We also calculate the spin-independent cross section
of the dark matter particle off with nucleon and discuss implications for
future direct dark matter search experiments.Comment: 13 pages, 4 figure
Minimal Flavor Violation in the Minimal U(1)_{B-L} Model and Resonant Leptogenesis
We investigate the resonant leptogenesis scenario in the minimally
extended standard model with minimal flavor violation. In our
model, the gauge symmetry is broken at the TeV scale and standard
model singlet neutrinos gain Majorana masses of order TeV. In addition, we
introduce a flavor symmetry on the singlet neutrinos at a scale higher than
TeV. The flavor symmetry is explicitly broken by the neutrino Dirac Yukawa
coupling, which induces splittings in the singlet neutrino Majorana masses at
lower scales through renormalization group evolutions. We call this setup
"minimal flavor violation". The mass-splittings are proportional to the tiny
Dirac Yukawa coupling, and hence they automatically enhance the CP asymmetry
parameter necessary for the resonant leptogenesis mechanism. In this paper, we
calculate the baryon number yield by solving the Boltzmann equations, including
the effects of gauge boson that also has TeV scale mass and causes
washing-out of the singlet neutrinos in the course of thermal leptogenesis. The
Dirac Yukawa coupling for neutrinos is fixed in terms of neutrino oscillation
data and an arbitrary complex-valued orthogonal matrix. We show
that the right amount of baryon number asymmetry can be achieved through
thermal leptogenesis in the context of the minimal flavor violation with
singlet neutrinos and gauge boson at the TeV scale. These
particles can be discovered at the LHC in the near future
Resonant Leptogenesis in the Minimal B-L Extended Standard Model at TeV
We investigate the resonant leptogenesis scenario in the minimal B-L extended
standard model(SM) with the B-L symmetry breaking at the TeV scale. Through
detailed analysis of the Boltzmann equations, we show how much the resultant
baryon asymmetry via leptogenesis is enhanced or suppressed, depending on the
model parameters, in particular, the neutrino Dirac Yukawa couplings and the
TeV-scale Majorana masses of heavy degenerate neutrinos. In order to consider a
realistic case, we impose a simple ansatz for the model parameters and analyze
the neutrino oscillation parameters and the baryon asymmetry via leptogenesis
as a function of only a single CP-phase. We find that for a fixed CP-phase all
neutrino oscillation data and the observed baryon asymmetry of the present
universe can be simultaneously reproduced.Comment: 25 pages, 15 figures, version to be published in Phys. Rev.
Formation of naked singularities in five-dimensional space-time
We numerically investigate the gravitational collapse of collisionless
particles in spheroidal configurations both in four and five-dimensional (5D)
space-time. We repeat the simulation performed by Shapiro and Teukolsky (1991)
that announced an appearance of a naked singularity, and also find that the
similar results in 5D version. That is, in a collapse of a highly prolate
spindle, the Kretschmann invariant blows up outside the matter and no apparent
horizon forms. We also find that the collapses in 5D proceed rapidly than in
4D, and the critical prolateness for appearance of apparent horizon in 5D is
loosened compared to 4D cases. We also show how collapses differ with spatial
symmetries comparing 5D evolutions in single-axisymmetry, SO(3), and those in
double-axisymmetry, U(1)U(1).Comment: 5 pages, 5 figures, To be published in Phys. Rev.
Pertumbuhan Isolat Phytophthora Infestans (Mont.) De Bary Tanaman Kentang Dan Tomat Pada Berbeda Media Di Laboratorium
The growth of Phytophthora infestans (Mont.) de Bary isolate of potato and tomato ondifferent media at Laboratory. This Research was to study the growth of P. infestans on differentmedia at Laboratory. This research was done in Laboratory of Plant disease, AgroecotechnologyProgram Study, Faculty of Agriculture, University of Sumatera Utara, Medan from July toDecember 2012. The method of This research was Completely Randomized Design Factorial withtwelve combinations and two replications. The results showed that the easiest growth isolate ofP. infestans on media was founded potato tubers (I2). The Best growth media of P. infestans wasfounded on media TEA (M3). The fastest growth and diameter of P. infestans was founded inpotato tubers on media TEA (I2M3) and slowest in the potato tubers isolates on PDA (I2M1).Macroscopic and microscopic morphology all isolates are completely same
Reconstructing the XUV Spectra of Active Sun-like Stars Using Solar Scaling Relations with Magnetic Flux
Kepler Space Telescope and Transiting Exoplanet Survey Satellite unveiled
that Sun-like stars frequently host exoplanets. These exoplanets are subject to
fluxes of ionizing radiation in the form of X-ray and extreme-ultraviolet (EUV)
radiation that may cause changes in their atmospheric dynamics and chemistry.
While X-ray fluxes can be observed directly, EUV fluxes cannot be observed
because of severe interstellar medium absorption. Here, we present a new
empirical method to estimate the whole stellar XUV (X-ray plus EUV) and FUV
spectra as a function of total unsigned magnetic fluxes of stars. The response
of the solar XUV and FUV spectrum (0.1-180 nm) to the solar total unsigned
magnetic flux is investigated by using the long-term Sun-as-a-star dataset over
10 yrs, and the power-law relation is obtained for each wavelength with a
spectral resolution of 0.1-1 nm. We applied the scaling relations to active
young Sun-like stars (G-dwarfs), EK Dra (G1.5V), Uma (G1.5V) and
Ceti (G5V), and found that the observed spectra (except for the
unobservable longward EUV wavelength) are roughly consistent with the extension
of the derived power-law relations with errors of an order of magnitude. This
suggests that our model is a valuable method to derive the XUV/FUV fluxes of
Sun-like stars including the EUV band mostly absorbed at wavelengths longward
of 36 nm. We also discuss differences between the solar extensions and stellar
observations at the wavelength in the 2-30 nm band and concluded that
simultaneous observations of magnetic and XUV/FUV fluxes are necessary for
further validations.Comment: 29 pages, 10 figures, 8 tables. Accepted for publication in The
Astrophysical Journa
CTX: A Clock-Gating-Based Test Relaxation and X-Filling Scheme for Reducing Yield Loss Risk in At-Speed Scan Testing
At-speed scan testing is susceptible to yield loss risk due to power supply noise caused by excessive launch switching activity. This paper proposes a novel two-stage scheme, namely CTX (Clock-Gating-Based Test Relaxation and X-Filling), for reducing switching activity when test stimulus is launched. Test relaxation and X-filling are conducted (1) to make as many FFs inactive as possible by disabling corresponding clock-control signals of clock-gating circuitry in Stage-1 (Clock-Disabling), and (2) to make as many remaining active FFs as possible to have equal input and output values in Stage-2 (FF-Silencing). CTX effectively reduces launch switching activity, thus yield loss risk, even with a small number of donpsilat care (X) bits as in test compression, without any impact on test data volume, fault coverage, performance, and circuit design.2008 17th Asian Test Symposium (ATS 2008), 24-27 November 2008, Sapporo, Japa
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