1,528 research outputs found
Five-dimensional Trinification Improved
We present improved models of trinification in five dimensions. Unified
symmetry is broken by a combination of orbifold projections and a boundary
Higgs sector. The latter can be decoupled from the theory, realizing a
Higgsless limit in which the scale of exotic massive gauge fields is set by the
compactification radius. Electroweak Higgs doublets are identified with the
fifth components of gauge fields and Yukawa interactions arise via Wilson
loops. The result is a simple low-energy effective theory that is consistent
with the constraints from proton decay and gauge unification.Comment: 13 pages LaTeX. v2: reference adde
An algorithm for correcting CoRoT raw light curves
We introduce the CoRoT detrend algorithm (CDA) for detrending CoRoT stellar
light curves. The algorithm CDA has the capability to remove random jumps and
systematic trends encountered in typical CoRoT data in a fully automatic
fashion. Since enormous jumps in flux can destroy the information content of a
light curve, such an algorithm is essential. From a study of 1030 light curves
in the CoRoT IRa01 field, we developed three simple assumptions which upon CDA
is based. We describe the algorithm analytically and provide some examples of
how it works. We demonstrate the functionality of the algorithm in the cases of
CoRoT0102702789, CoRoT0102874481, CoRoT0102741994, and CoRoT0102729260. Using
CDA in the specific case of CoRoT0102729260, we detect a candidate exoplanet
around the host star of spectral type G5, which remains undetected in the raw
light curve, and estimate the planetary parameters to be Rp=6.27Re and P=1.6986
days.Comment: 8 pages, 13 figure
Holographic Electroweak Symmetry Breaking from D-branes
We observe several interesting phenomena in a technicolor-like model of
electroweak symmetry breaking based on the D4-D8-D8bar system of Sakai and
Sugimoto. The benefit of holographic models based on D-brane configurations is
that both sides of the holographic duality are well understood. We find that
the lightest technicolor resonances contribute negatively to the
Peskin-Takeuchi S-parameter, but heavy resonances do not decouple and lead
generically to large, positive values of S, consistent with standard estimates
in QCD-like theories. We study how the S parameter and the masses and decay
constants of the vector and axial-vector techni-resonances vary over a
one-parameter family of D8-brane configurations. We discuss possibilities for
the consistent truncation of the theory to the first few resonances and suggest
some generic predictions of stringy holographic technicolor models.Comment: REVTeX, 25 pages, 8 eps figures, version published in PR
Orthogonal U(1)'s, Proton Stability and Extra Dimensions
In models with a low quantum gravity scale, one might expect that all
operators consistent with gauge symmetries are present in the low-energy
effective theory. If this is the case, some mechanism must be present to
adequately suppress operators that violate baryon number. Here we explore the
possibility that the desired suppression is a consequence of an additional,
spontaneously-broken, non-anomalous U(1) symmetry that is orthogonal to
hypercharge. We show that successful models can be constructed in which the
additional particle content necessary to cancel anomalies is minimal, and
compatible with the constraints from precision electroweak measurements and
gauge unification. If unification is sacrificed, and only the new U(1) and its
associated Higgs fields live in the bulk, it is possible that the gauge field
zero mode and first few Kaluza-Klein excitations lie within the kinematic reach
of the Tevatron. For gauge couplings not much smaller than that of hypercharge,
we show that these highly leptophobic states could evade detection at Run I,
but be discovered at Run II. Our scenario presents an alternative to the
`cartographic' solution to baryon number violation in which leptons and quarks
are separated in an extra dimension.Comment: 16 pages LaTeX, 4 figure
Deconstructing Superconductivity
We present a dimensionally deconstructed model of an s-wave holographic
superconductor. The 2+1 dimensional model includes multiple charged Cooper pair
fields and neutral exciton fields that have interactions governed by hidden
local symmetries. We derive AdS/CFT-like relations for the current and charge
density in the model, and we analyze properties of the Cooper pair condensates
and the complex conductivity.Comment: 24 pages, 10 eps figures. v2: Sign conventions clarified, references
adde
Higgsless GUT Breaking and Trinification
Boundary conditions on an extra-dimensional interval can be chosen to break
bulk gauge symmetries and to reduce the rank of the gauge group. We consider
this mechanism in models with gauge trinification. We determine the boundary
conditions necessary to break the trinified gauge group directly down to that
of the standard model. Working in an effective theory for the gauge
symmetry-breaking parameters on a boundary, we examine the limit in which the
GUT-breaking sector is Higgsless and show how one may obtain the low-energy
particle content of the minimal supersymmetric standard model. We find that
gauge unification is preserved in this scenario, and that the differential
gauge coupling running is logarithmic above the scale of compactification. We
compare the phenomenology of our model to that of four-dimensional trinified
theories.Comment: 22 pages, LaTeX, 2 eps figures (v3: discussion of mass scales
clarified
Italian adaptation and psychometric properties of the prejudice against immigrants scale (PAIS): assessment of validity, reliability, and measure invariance
The aim of the current study was to adapt and validate the Prejudice Against Immigrants Scale (PAIS) in the Italian context, based on the Prejudice Against Asylum Seekers Scale by Anderson (2018). The validity, reliability, and measurement invariance across gender, age, and educational levels of the scale were assessed through three sources, which involved 306 Italian individuals (Nmen = 151, 49.3%) between 18 and 60 years old. Both exploratory and confirmatory factor analyses (CFA) confirmed the two-factor solution of the original instrument by excluding two items, which were present in the previous validation study. The first factor is classical prejudice against immigrants, which maps onto theoretical derivations of classical and old-fashioned prejudices, whereas the second factor is conditional prejudice against immigrants, which maps onto theoretical derivations of subtle and modern prejudices. Findings of the multigroup CFAs demonstrated full configural and metric invariance and partial scalar invariance of the scale across gender, age, and educational level. The analyses confirmed that PAIS has high levels of reliability and criterion and construct validity, showing findings that are comparable to those of Anderson (2018). These results suggest that PAIS presents very good psychometric properties and could be considered a valid and reliable instrument to measure prejudice against immigrants, by enabling Italian researchers to detect both covert and more subtle forms of prejudice against immigrants. Limitations and further directions are discussed
The influence of planetary engulfment on stellar rotation in metal-poor main-sequence stars
The method of gyrochronology relates the age of its star to its rotation
period. However, recent evidence of deviations from gyrochronology relations
was reported in the literature. Here, we study the influence of tidal
interaction between a star and its companion on the rotation velocity of the
star, in order to explain peculiar stellar rotation velocities. The interaction
of a star and its planet is followed using a comprehensive numerical framework
that combines tidal friction, magnetic braking, planet migration, and detailed
stellar evolution models from the GARSTEC grid. We focus on close-in companions
from 1 to 20 M orbiting low-mass, 0.8 and 1 M, main-sequence
stars with a broad metallicity range from [Fe/H] = -1 to solar. Our simulations
suggest that the dynamical interaction between a star and its companion can
have different outcomes, which depend on the initial semi-major axis and the
mass of the planet, as well as the mass and metallicity of its host star. In
most cases, especially in the case of planet engulfment, we find a catastrophic
increase in stellar rotation velocity from 1 kms to over 40 kms,
while the star is still on the main-sequence. The main prediction of our model
is that low-mass main-sequence stars with abnormal rotation velocities should
be more common at low-metallicity, as lower [Fe/H] favours faster planet
engulfment, provided occurrence rate of close in massive planets is similar at
all metallicities. Our scenario explains peculiar rotation velocities of
low-mass main-sequence stars by the tidal interaction between the star and its
companion. Current observational samples are too small and incomplete, and thus
do not allow us to test our model.Comment: 10 pages, 6 figures, accepted for publication in A&
Bulk Majorons at Colliders
Lepton number violation may arise via the spontaneous breakdown of a global
symmetry. In extra dimensions, spontaneous lepton number violation in the bulk
implies the existence of a Goldstone boson, the majoron J^(0), as well as an
accompanying tower of Kaluza-Klein (KK) excitations, J^(n). Even if the
zero-mode majoron is very weakly interacting, so that detection in low-energy
processes is difficult, the sum over the tower of KK modes may partially
compensate in processes of relevance at high-energy colliders. Here we consider
the inclusive differential and total cross sections for e^- e^- --> W^- W^- J,
where J represents a sum over KK modes. We show that allowed parameter choices
exist for which this process may be accessible to a TeV-scale electron
collider.Comment: 11 pages LaTeX, 3 eps figures (references added
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