11,528 research outputs found
Exploring the Vacuum Geometry of N=1 Gauge Theories
Using techniques of algorithmic algebraic geometry, we present a new and
efficient method for explicitly computing the vacuum space of N=1 gauge
theories. We emphasize the importance of finding special geometric properties
of these spaces in connecting phenomenology to guiding principles descending
from high-energy physics. We exemplify the method by addressing various
subsectors of the MSSM. In particular the geometry of the vacuum space of
electroweak theory is described in detail, with and without right-handed
neutrinos. We discuss the impact of our method on the search for evidence of
underlying physics at a higher energy. Finally we describe how our results can
be used to rule out certain top-down constructions of electroweak physics.Comment: 35 pages, 2 figures, LaTe
Vacuum Geometry and the Search for New Physics
We propose a new guiding principle for phenomenology: special geometry in the
vacuum space. New algorithmic methods which efficiently compute geometric
properties of the vacuum space of N=1 supersymmetric gauge theories are
described. We illustrate the technique on subsectors of the MSSM. The fragility
of geometric structure that we find in the moduli space motivates
phenomenologically realistic deformations of the superpotential, while arguing
against others. Special geometry in the vacuum may therefore signal the
presence of string physics underlying the low-energy effective theory.Comment: 8 pages, LaTeX; v2: revised title, minor changes in wording,
reference adde
Unitarity of Little Higgs Models Signals New Physics of UV Completion
The ``Little Higgs'' opens up a new avenue for natural electroweak symmetry
breaking in which the standard model Higgs particle is realized as a
pseudo-Goldstone boson and thus is generically light. The symmetry breaking
structure of the Little Higgs models predicts a large multiplet of
(pseudo-)Goldstone bosons and their low energy interactions below the
ultraviolet (UV) completion scale TeV, where
is the Goldstone decay constant. We study unitarity of the Little Higgs
models by systematically analyzing the high energy scatterings of these
(pseudo-)Goldstone bosons. We reveal that the collective effect of the
Goldstone scatterings via coupled channel analysis tends to push the unitarity
violation scale significantly below the conventional UV scale
as estimated by naive dimensional analysis (NDA).
Specifically, , lying in the multi-TeV range for TeV. We interpret this as an encouraging sign that the upcoming LHC may
explore aspects of Little Higgs UV completions, and we discuss some potential
signatures. The meanings of the two estimated UV scales (from
unitarity violation) and (from NDA) together with their implications
for an effective field theory analysis of the Little Higgs models are also
discussed.Comment: To match Phys.Lett.B version (9pp, only minor rewording
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Immunosuppressive effect and global dysregulation of blood transcriptome in response to psychosocial stress in vervet monkeys (Chlorocebus sabaeus).
Psychosocial stressors - life events that challenge social support and relationships - represent powerful risk factors for human disease; included amongst these events are relocation, isolation and displacement. To evaluate the impact of a controlled psychosocial stressor on physiology and underlying molecular pathways, we longitudinally studied the influence of a 28-day period of quarantine on biomarkers of immune signalling, microbial translocation, glycaemic health and blood transcriptome in the wild-born vervet monkey. This event caused a coordinated, mostly transient, reduction of circulating levels of nine immune signalling molecules. These were paralleled by a massive dysregulation of blood transcriptome, including genes implicated in chronic pathologies and immune functions. Immune and inflammatory functions were enriched among the genes downregulated in response to stress. An upregulation of genes involved in blood coagulation, platelet activation was characteristic of the rapid response to stress induction. Stress also decreased neutrophils and increased CD4â+âT cell proportions in blood. This model of psychosocial stress, characterised by an immune dysregulation at the transcriptomic, molecular and cellular levels, creates opportunities to uncover the underlying mechanisms of stress-related diseases with an immune component, including cardiovascular diseases and susceptibility to infections
The Geometry of Generations
We present an intriguing and precise interplay between algebraic geometry and the phenomenology of generations of particles. Using the electroweak sector of the MSSM as a testing ground, we compute the moduli space of vacua as an algebraic variety for multiple generations of Standard Model matter and Higgs doublets. The space is shown to have CalabiâYau, Grassmannian, and toric signatures, which sensitively depend on the number of generations of leptons, as well as inclusion of Majorana mass terms for right-handed neutrinos. We speculate as to why three generations is special
Experimental determination of superconducting parameters for the intermetallic perovskite superconductor ${\text {MgCNi}}_3
We have measured upper-critical-field , specific heat C, and
tunneling spectra of the intermetallic perovskite superconductor MgCNi
with a superconducting transition temperature K. Based
on these measurements and relevant theoretical relations, we have evaluated
various superconducting parameters for this material, including the
thermodynamic critical field (0), coherence length (0),
penetration depth (0), lower-critical-field (0), and
Ginsberg-Landau parameter (0). From the specific heat, we obtain the
Debye temperature 280 K. We find a jump of
=2.3 at (where is the
normal state electronic specific coefficient), which is much larger than the
weak coupling BCS value of 1.43. Our tunneling measurements revealed a gap
feature in the tunneling spectra at with 4.6, again larger than the weak-coupling value
of 3.53. Both findings indicate that MgCNi is a strong-coupling
superconductor. In addition, we observed a pronounced zero-bias conductance
peak (ZBCP) in the tunneling spectra.
We discuss the possible physical origins of the observed ZBCP, especially in
the context of the pairing symmetry of the material.Comment: 5 pages, 4 figure
Fermionic anticommutators for open superstrings in the presence of antisymmetric tensor field
We build up the anticommutator algebra for the fermionic coordinates of open
superstrings attached to branes with antisymmetric tensor fields. We use both
Dirac quantization and the symplectic Faddeev Jackiw approach. In the
symplectic case we find a way of generating the boundary conditions as zero
modes of the symplectic matrix by taking a discretized form of the action and
adding terms that vanish in the continuous limit. This way boundary conditions
can be handled as constraints.Comment: Revision: passage from discrete to continuous clarified, comment on
previous results using Dirac quantization included, typos corrected. Version
to appear in Phys. Lett.
Longitudinal Analysis of T-Cell Receptor Variable ÎČ Chain Repertoire in Patients with Acute Graft-versus-Host Disease after Allogeneic Stem Cell Transplantation
AbstractT-cell receptor variable ÎČ chain (TCRBV) repertoire spectratyping involves the estimation of CDR3 length distributions for monitoring T-cell receptor diversity and has proven useful for analyses of immune reconstitution and T-cell clonal expansions in graft-versus-host disease (GVHD) and graft-versus-leukemia after allogeneic stem cell transplantation. We performed a longitudinal spectratype analysis of 23 TCRBV families in 28 patients who underwent allogeneic T cellâdepleted peripheral blood stem cell transplantation. Sixteen patients subsequently developed acute GVHD. We recently developed statistical methods that bring increased power and flexibility to spectratype analysis and allow us to analyze TCRBV repertoire development under appropriately complex statistical models. Applying these methods, we found that patients with acute GVHD demonstrated TCRBV repertoire development statistically distinct from that repertoire development in patients without GVHD. Specifically, GVHD patients showed spectratypes indicative of lower diversity and greater deviation from the spectratypes expected in healthy individuals at intermediate times. Most individual TCRBV subfamilies had spectratypes statistically distinguishable between GVHD and non-GVHD patients at 6 months after transplantation. These results suggest that the T-cell receptor repertoire perturbations associated with acute GVHD are widely spread throughout the TCRBV families
Variability of Broad and Blueshifted Component of [OIII]5007 in IZWI
Although the existence of asymmetrical profile of [OIII]5007 has
been discovered for ages, its filiation and physics are poorly understood. Two
new spectra of I ZWI taken on Nov 16, 2001 and on Dec 3, 2002 were compared
with the spectra taken by BG92. Following results are obtained. 1)The certain
variations of broad [OIII] during about 10 years separating the observations
are identified. The inferred length scale of broad [OIII] emitting region
ranges from 0.3pc to 3pc. By assuming a Keplerian motion in emitting region,
the material emitting broad [OIII] is likely to be located at transient
emission line region, between BLR and NLR. 2)We find a positive relation
between the FeII emission and flux of H(or continuum). On the other
hand, the parameter RFe decreases with ionizing continuum marginally. 3)We
detect a low ionized NLR in I ZWI, because of the low flux ratios
().Comment: 14 pages, 3 figures, NewA in pres
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