3,083 research outputs found
Product Groups, Discrete Symmetries, and Grand Unification
We study grand unified theories based on an SU(5)xSU(5) gauge group in which
the GUT scale, M_{GUT}, is the VEV of an exact or approximate modulus, and in
which fast proton decay is avoided through a combination of a large triplet
mass and small triplet couplings. These features are achieved by discrete
symmetries. In many of our models, M_{GUT} is generated naturally by the
balance of higher dimension terms that lift the GUT modulus potential, and soft
supersymmetry breaking masses. The theories often lead to interesting patterns
of quark and lepton masses. We also discuss some distinctions between grand
unified theories and string unification.Comment: 23 pages; no figures; revtex
Electroweak precision constraints on the Lee-Wick Standard Model
We perform an analysis of the electroweak precision observables in the
Lee-Wick Standard Model. The most stringent restrictions come from the S and T
parameters that receive important tree level and one loop contributions. In
general the model predicts a large positive S and a negative T. To reproduce
the electroweak data, if all the Lee-Wick masses are of the same order, the
Lee-Wick scale is of order 5 TeV. We show that it is possible to find some
regions in the parameter space with a fermionic state as light as 2.4-3.5 TeV,
at the price of rising all the other masses to be larger than 5-8 TeV. To
obtain a light Higgs with such heavy resonances a fine-tuning of order a few
per cent, at least, is needed. We also propose a simple extension of the model
including a fourth generation of Standard Model fermions with their Lee-Wick
partners. We show that in this case it is possible to pass the electroweak
constraints with Lee-Wick fermionic masses of order 0.4-1.5 TeV and Lee-Wick
gauge masses of order 3 TeV.Comment: 24 pages, 7 figure
Classical electromagnetic field theory in the presence of magnetic sources
Using two new well defined 4-dimensional potential vectors, we formulate the
classical Maxwell's field theory in a form which has manifest Lorentz
covariance and SO(2) duality symmetry in the presence of magnetic sources. We
set up a consistent Lagrangian for the theory. Then from the action principle
we get both Maxwell's equation and the equation of motion of a dyon moving in
the electro-magnetic field.Comment: 10 pages, no figure
Restricted Diffusion of Pus in the Subarachnoid Space: MRSA Meningo-Vasculitis and Progressive Brainstem Ischemic Strokes – A Case Report
Extra-axial restriction on diffusion weighted imaging (DWI) is an unusual finding on brain magnetic resonance imaging (MRI). Intra-axial restriction on DWI, however, is common, and can represent brain parenchymal infarction, tumor, abscess, or toxic-metabolic process. The infrequency of extra-axial DWI restriction and the paucity of clinico-pathological correlation in the literature limit its differential diagnosis. Scant case reports suggest that extra-axial DWI restriction could be a lymphoma, neurenteric cyst, or, in one patient, subdural empyema [1,2,3]. We postulate that pus formation must be excluded first, because it can provoke an aggressive meningo-vasculitis with rapidly fatal, intra-axial infarctions. Our patient was a 45-year-old man, presenting to our hospital with left facial droop and right (contralateral) arm and leg weakness. Initial MRI revealed DWI restriction in the left lateral pons, consistent with a classic Millard-Gubler stroke. Also noted was a subtle, extra-axial area of curvilinear diffusion restriction in the left cerebellar-pontine angle's subarachnoid space. Days later, the patient had a headache, and repeat MRI revealed extension of the two DWI lesions – both the intra-axial pontine infarction and the extra-axial area of restricted diffusion in the subarachnoid space. The patient became comatose, a third MRI revealed more extensive DWI restrictions, and he expired despite aggressive care. Autopsy revealed massive brainstem infarcts, a thick lymphoplasmacytic infiltrate, copious Gram-Positive cocci (likely MRSA) and arteries partially occluded with fibrointimal proliferation. This emphasizes the concept that extra-axial DWI restriction can represent pus development in the subarachnoid space – a radiographic marker to identify a patient at risk for demise due to septic, meningo-vasculitic infarctions
Supersymmetric sound in fluids
We consider the hydrodynamics of supersymmetric fluids. Supersymmetry is
broken spontaneously and the low energy spectrum includes a fermionic massless
mode, the . We use two complementary approaches to describe
the system: First, we construct a generating functional from which we derive
the equations of motion of the fluid and of the phonino propagating through the
fluid. We write the form of the leading corrections in the derivative
expansion, and show that the so called diffusion terms in the supercurrent are
in fact not dissipative. Second, we use an effective field theory approach
which utilizes a non-linear realization of supersymmetry to analyze the
interactions between phoninos and phonons, and demonstrate the conservation of
entropy in ideal fluids. We comment on possible phenomenological consequences
for gravitino physics in the early universe.Comment: Modified introduction and discussion of diffusion terms in the
supercurren
Preferencias y aceptabilidad de los consumidores por la carne de vacuno enriquecida en omega-3 y ácido linoleico conjugado en tres ciudades españolas
Este trabajo analiza las preferencias de los consumidores en tres ciudades españolas
(Barcelona, Zaragoza y Pamplona) con el objetivo de estimar la importancia relativa de los atributos
más relevantes de la carne de vacuno incluyendo su enriquecimiento con ácidos grasos no
saturados como el omega-3 (n-3) y el ácido linoleico conjugado (CLA). Asimismo, se pretende estudiar
el impacto de la experiencia sensorial y la información sobre las preferencias y la heterogeneidad
no observada tanto del factor de escala como de los atributos. Los datos fueron recogidos
de un cuestionario estructurado y auto-completado en un ambiente controlado con dos muestras
diferentes (320 y 325 consumidores) diferenciados por la información recibida. El experimento
de elección fue aplicado antes y después de que los mismos consumidores evaluaran la aceptabilidad
de la carne enriquecida. Para el análisis de datos se ha empleado el modelo Multinomial
Generalizado (GMNL). Los resultados mostraron un impacto significativo de la información y la
experiencia sensorial sobre las preferencias. La utilidad de la carne enriquecida con n-3 en las tres
ciudades se incrementó significativamente después de probar la carne, sobre todo para los consumidores
que no recibieron información, mientras que la utilidad de la carne enriquecida con CLA
no fue significativa independientemente de la evaluación hedónica o la información proporcionada.
Después de la experiencia sensorial, la heterogeneidad de escala, que es la variación del grado de
aleatoriedad en el proceso de toma de decisiones y por lo tanto el grado de certeza de los individuos
en sus elecciones, ha disminuido significativamente. Finalmente, los resultados mostraron
un aumento de la aceptabilidad global de la carne enriquecida con n-3 y CLA respecto a la carne
convencional y la información ofrecida a los consumidores no tuvo ningún impacto significativo en
sus puntuaciones.Publishe
3-(2,4-Dibromoanilino)-2,2-dimethyl-2,3-dihydronaphtho[1,2-b]furan-4,5-dione: a new substituted arylamino nor-β-lapachone derivative
The title compound, C20H15Br2NO3, shows the furan ring to adopt a half-chair conformation and the two ring systems to be approximately perpendicular [dihedral angle = 71.0 (2)°]. In the crystal structure, intermolecular C—H⋯O contacts link the molecules
Onset of dissipation in ballistic atomic wires
Electronic transport at finite voltages in free-standing gold atomic chains
of up to 7 atoms in length is studied at low temperatures using a scanning
tunneling microscope (STM). The conductance vs voltage curves show that
transport in these single-mode ballistic atomic wires is non-dissipative up to
a finite voltage threshold of the order of several mV. The onset of dissipation
and resistance within the wire corresponds to the excitation of the atomic
vibrations by the electrons traversing the wire and is very sensitive to
strain.Comment: Revtex4, 4 pages, 3 fig
Three form potential in (special) minimal supergravity superspace and supermembrane supercurrent
This contribution begins the study of the complete superfield Lagrangian
description of the interacting system of D=4 N=1 supergravity (SUGRA) and
supermembrane. Firstly, we review a 'three form supergravity' by Ovrut and
Waldram, which we prefer to call 'special minimal supergravity'. This off-shell
formulation of simple SUGRA is appropriate for our purposes as the
supermembrane action contains the so-called Wess-Zumino term given by the
integral over a three form potential in superspace, C3. We describe this
formulation in the frame of Wess--Zumino superfield approach, showing how the
basic variations of minimal SUGRA are restricted by the conditions of the
existence of a three-form potential C3 in its superspace. In this language the
effect of dynamical generation of cosmological constant, known to be
characteristic for this formulation of SUGRA, appears in its superfield form,
first described by Ogievetsky and Sokatchev in their formulation of SUGRA as a
theory of axial vector superfield. Secondly, we vary the supermembrane action
with respect to the special minimal SUGRA superfields (basic variations) and
obtain the supercurrent superfields as well as the supergravity superfield
equations with the supermembrane contributions.Comment: 18 pages, no figures. V2: Important references added. The abstract
and presentation have been changed to reflect the overloop with that.
Submitted to the QTS7 Proceedings. J. Phys. style use
- …