2,392 research outputs found
D-brane Inspired Fermion Mass Textures
In this paper, the issues of the quark mass hierarchies and the Cabbibo
Kobayashi Maskawa mixing are analyzed in a class of intersecting D-brane
configurations with Standard Model gauge symmetry. The relevant mass matrices
are constructed taking into account the constraints imposed by extra abelian
symmetries and anomaly cancelation conditions. Possible mass generating
mechanisms including perturbative as well as non-perturbative effects are
discussed and specific patterns of mass textures are found characterized by the
hierarchies of the scales where the various sources contribute. It is argued
that the Cholesky decomposition of the mass matrices is the most appropriate
way to determine the properties of these fermion mass patterns, while the
associated triangular mass matrix form provides a unified description of all
phenomenologically equivalent symmetric and non-symmetric mass matrices. An
elegant analytic formula is derived for the Cholesky triangular form of the
mass matrices where the entries are given as simple functions of the mass
eigenstates and the diagonalizing transformation entries. Finally, motivated by
the possibility of vanishing zero Yukawa mass entries in several D-brane and
F-theory constructions due to the geometry of the internal space, we analyse in
detail all possible texture-zeroes mass matrices within the proposed new
context. These new texture-zeroes are compared to those existing in the
literature while D-brane inspired cases are worked out in detail.Comment: 58 pages, 7 figure
Discrete symmetries and isosinglet quarks in low-energy supersymmetry
Many extensions of the minimal supersymmetric standard model contain
superfields for quarks which are singlets under weak isospin with electric
charge -1/3. We explore the possibility that such isosinglet quarks have low or
intermediate scale masses, but do not mediate rapid proton decay because of a
discrete symmetry. By imposing the discrete gauge anomaly cancellation
conditions, we show that the simplest way to achieve this is to extend the Z_3
"baryon parity" of Ibanez and Ross to the isosinglet quark superfields. This
can be done in three distinct ways. This strategy is not consistent with grand
unification with a simple gauge group, but may find a natural place in
superstring-inspired models, for example. An interesting feature of this
scenario is that proton decay is absolutely forbidden.Comment: 13 pages, MIT-CTP-2345, NUB-3097-94T
Generalized Linear Models for Geometrical Current predictors. An application to predict garment fit
The aim of this paper is to model an ordinal response variable in terms
of vector-valued functional data included on a vector-valued RKHS. In particular,
we focus on the vector-valued RKHS obtained when a geometrical object (body) is
characterized by a current and on the ordinal regression model. A common way to
solve this problem in functional data analysis is to express the data in the orthonormal
basis given by decomposition of the covariance operator. But our data present very important differences with respect to the usual functional data setting. On the one
hand, they are vector-valued functions, and on the other, they are functions in an
RKHS with a previously defined norm. We propose to use three different bases: the
orthonormal basis given by the kernel that defines the RKHS, a basis obtained from
decomposition of the integral operator defined using the covariance function, and a
third basis that combines the previous two. The three approaches are compared and
applied to an interesting problem: building a model to predict the fit of children’s
garment sizes, based on a 3D database of the Spanish child population. Our proposal
has been compared with alternative methods that explore the performance of other
classifiers (Suppport Vector Machine and k-NN), and with the result of applying
the classification method proposed in this work, from different characterizations of
the objects (landmarks and multivariate anthropometric measurements instead of
currents), obtaining in all these cases worst results
Baryogenesis, Dark Matter and the Pentagon
We present a new mechanism for baryogenesis, which links the baryon asymmetry
of the universe to the dark matter density. The mechanism arises naturally in
the Pentagon model of TeV scale physics. In that context, it forces a
re-evaluation of some of the assumptions of the model, and we detail the
changes that are required in order to fit observations.Comment: JHEP3 LaTeX, 15 pages. New version corrects errors in the electroweak
baryon violating and matter radiation temperatures, which were pointed out by
the referee. Substantial quantitative but no qualitative change to our
conclusion
Entanglement of excited states in critical spin chians
Renyi and von Neumann entropies quantifying the amount of entanglement in
ground states of critical spin chains are known to satisfy a universal law
which is given by the Conformal Field Theory (CFT) describing their scaling
regime. This law can be generalized to excitations described by primary fields
in CFT, as was done in reference (Alcaraz et. al., Phys. Rev. Lett. 106, 201601
(2011)), of which this work is a completion. An alternative derivation is
presented, together with numerical verifications of our results in different
models belonging to the c=1,1/2 universality classes. Oscillations of the Renyi
entropy in excited states and descendant fields are also discussed.Comment: 23 pages, 13 figure
The Evolution of Destination Branding: A Review of Branding Literature in Tourism
Tourism is a promise and destinations communicate the credibility of that promise by means of destination brands. Branding has become a key tool for tourism destinations to make explicit the complexity of experiences to be expected by tourists visiting a destination. This paper provides a comprehensive literature review of various issues associated with tourism destination branding. It brings together a wide range of debates in the generic marketing literature, places them alongside the nuances of tourism, and thereby identifies unique challenges of branding in tourism destination contexts. Finally, a case study of USP based national tourism branding campaigns in the Caribbean is presented
Dynamical supersymmetry breaking in models with a Green-Schwarz mechanism
We consider supersymmetry breaking in theories with gaugino condensation in
the presence of an anomalous U(1) symmetry with anomaly cancellation by the
Green-Schwarz mechanism. In these models, a Fayet-Iliopoulos D-term can give
important contributions to the soft supersymmetry-breaking scalar masses. Most
discussions of this possibility have ignored the dilaton field. We argue that
this is not appropriate in general, and show that the F-term contributions to
the soft breaking terms are comparable to or much larger than the D-term
contributions, depending on how the dilaton is stabilized. We discuss
phenomenological implications of these results.Comment: 14 pages, LaTe
Nonminimal supersymmetric standard model with lepton number violation
We carry out a detailed analysis of the nonminimal supersymmetric standard
model with lepton number violation. The model contains a unique trilinear
lepton number violating term in the superpotential which can give rise to
neutrino masses at the tree level. We search for the gauged discrete symmetries
realized by cyclic groups which preserve the structure of the associated
trilinear superpotential of this model, and which satisfy the constraints of
the anomaly cancellation. The implications of this trilinear lepton number
violating term in the superpotential and the associated soft supersymmetry
breaking term on the phenomenology of the light neutrino masses and mixing is
studied in detail. We evaluate the tree and loop level contributions to the
neutrino mass matrix in this model. We search for possible suppression
mechanism which could explain large hierarchies and maximal mixing angles.Comment: Latex file, 43 pages, 2 figure
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