33,352 research outputs found
Spontaneous symmetry breaking in the -symmetric scalar sector
We present a detailed study of the vacua of the -symmetric
three-Higgs-doublet potential, specifying the region of parameters where these
minimisation solutions occur. We work with a CP conserving scalar potential and
analyse the possible real and complex vacua with emphasis on the cases in which
the CP symmetry can be spontaneously broken. Results are presented both in the
reducible-representation framework of Derman, and in the
irreducible-representation framework. Mappings between these are given. Some of
these implementations can in principle accommodate dark matter and for that
purpose it is important to identify the residual symmetries of the potential
after spontaneous symmetry breakdown. We are also concerned with constraints
from vacuum stability.Comment: 37 pages. v2: Minor changes in the references, matches published
version. v3: Table 6 corrected: two additional cases conserve CP. Related
discussion adapted. Version consistent with JHEP Erratu
Spontaneous symmetry breaking in three-Higgs-doublet -symmetric models
The talk summarises work done by the authors consisting of a detailed study
of the possible vacua in models with three Higgs doublets with symmetry
and without explicit CP violation. Different vacua require special regions of
the parameter space which were analysed in our work. We establish the
possibility of spontaneous CP violation in this framework and we also show
which complex vacua conserve CP. In our work we discussed constraints from
vacuum stability. The results presented here are relevant for model building.Comment: 11 pages, no figures. Prepared for the proceedings of DISCRETE2016:
the Fifth Symposium on Prospects in the Physics of Discrete Symmetries, 28
November-3 December 2016, University of Warsaw, Poland, to appear in the
Journal of Physics: Conference Series (JPCS
Efficiency of low versus high airline pressure in stunning cattle with a pneumatically powered penetrating captive bolt gun
The efficiency of stunning cattle was assessed in 443 animals (304 pure Zebu and 139 crossbred cattle), being mainly mature bulls and cows. Cattle were stunned using a Jarvis pneumatically powered penetrating captive bolt gun operating with low (160–175 psi, N = 82) and high (190 psi, N = 363) airline pressure, which was within the manufactures specifications. Signs of brain function and the position of the shots on the heads were recorded after stunning. Velocity of the captive bolt and its physical parameters were calculated. Cattle shot with low pressures showed more rhythmic respiration (27 vs. 8%, P < 0.001), less tongue protrusion (4 vs. 12%, P = 0.03) and less masseter relaxation (22 vs. 48%, P < 0.001). There was an increased frequency of shots in the ideal position when cattle were shot with the low compared to high airline pressures (15.3 vs. 3.1%). Bolt velocity and its physical parameters were significantly (P < 0.01) higher when using high pressure. Airline pressures below 190 psi are inappropriate when shooting adult Zebu beef cattle with pneumatically powered penetrating captive bolt guns
Proton decay matrix elements with domain-wall fermions
Hadronic matrix elements of operators relevant to nucleon decay in grand
unified theories are calculated numerically using lattice QCD. In this context,
the domain-wall fermion formulation, combined with non-perturbative
renormalization, is used for the first time. These techniques bring reduction
of a large fraction of the systematic error from the finite lattice spacing.
Our main effort is devoted to a calculation performed in the quenched
approximation, where the direct calculation of the nucleon to pseudoscalar
matrix elements, as well as the indirect estimate of them from the nucleon to
vacuum matrix elements, are performed. First results, using two flavors of
dynamical domain-wall quarks for the nucleon to vacuum matrix elements are also
presented to address the systematic error of quenching, which appears to be
small compared to the other errors. Our results suggest that the representative
value for the low energy constants from the nucleon to vacuum matrix elements
are given as |alpha| simeq |beta| simeq 0.01 GeV^3. For a more reliable
estimate of the physical low energy matrix elements, it is better to use the
relevant form factors calculated in the direct method. The direct method tends
to give smaller value of the form factors, compared to the indirect one, thus
enhancing the proton life-time; indeed for the pi^0 final state the difference
between the two methods is quite appreciable.Comment: 56 pages, 17 figures, a comment and two references added in the
introduction, typo corrected in Eq.1
Supersymmetry breaking as the origin of flavor
We present an effective flavor model for the radiative generation of fermion
masses and mixings based on a SU(5)xU(2) symmetry. We assume that the original
source of flavor breaking resides in the supersymmetry breaking sector. Flavor
violation is transmitted radiatively to the fermion Yukawa couplings at low
energy through finite supersymmetric threshold corrections. This model can fit
the fermion mass ratios and CKM matrix elements, explain the non-observation of
proton decay, and overcome present constraints on flavor changing processes
through an approximate radiative alignment between the Yukawa and the soft
trilinear sector. The model predicts new relations between dimensionless
fermion mass ratios in the three fermion sectors, and the quark mixing angles.Comment: 14 pages, RevTex
Manejo da cultura do melao.
bitstream/item/136340/1/ID-8814.pdfApostila do I Curso sobre o Cultivo do Melao, 2000, Petrolina
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