70 research outputs found
One loop gauge couplings in AdS5
We calculate the full 1-loop corrections to the low energy coupling of bulk
gauge boson in a slice of AdS5 which are induced by generic 5-dimensional
scalar, Dirac fermion, and vector fields with arbitrary Z_2 times Z_2' orbifold
boundary conditions. In supersymmetric limit, our results correctly reproduce
the results obtained by an independent method based on 4-dimensional effective
supergravity. This provides a nontrivial check of our results and assures the
regularization scheme-independence of the results.Comment: RevTeX, 22 pages, 2 figures, some typos corrected and notations
change
Loop-Effects in Pseudo-Supersymmetry
We analyze the transmission of supersymmetry breaking in brane-world models
of pseudo-supersymmetry. In these models two branes preserve different halves
of the bulk supersymmetry. Thus supersymmetry is broken although each sector of
the model is supersymmetric when considered separately. The world-volume theory
on one brane feels the breakdown of supersymmetry only through two-loop
interactions involving a coupling to fields from the other brane. In a 5D toy
model with bulk vectors, we compute the diagrams that contribute to scalar
masses on one brane and find that the masses are proportional to the
compactification scale up to logarithmic corrections, m^2 ~ (2 pi R)^{-2}(ln(2
pi R ms)-1.1), where ms is an ultraviolet cutoff. Thus, for large
compactification radii, where this result is valid, the brane scalars acquire a
positive mass squared. We also compute the three-loop diagrams relevant to the
Casimir energy between the two branes and find E ~ (2 pi R)^{-4}((ln(2 pi R
ms)-1.7)^2+0.2). For large radii, this yields a repulsive Casimir force.Comment: Latex, 30 pages, 6 figures, v2: minor corrections, comments on susy
algebra and x^5 covariant derivative adde
The serum metabolome mediates the concert of diet, exercise, and neurogenesis, determining the risk for cognitive decline and dementia
Introduction: Diet and exercise influence the risk of cognitive decline (CD) and dementia through the food metabolome and exercise-triggered endogenous factors, which use the blood as a vehicle to communicate with the brain. These factors might act in concert with hippocampal neurogenesis (HN) to shape CD and dementia. Methods: Using an in vitro neurogenesis assay, we examined the effects of serum samples from a longitudinal cohort (n = 418) on proxy HN readouts and their association with future CD and dementia across a 12-year period. Results: Altered apoptosis and reduced hippocampal progenitor cell integrity were associated with exercise and diet and predicted subsequent CD and dementia. The effects of exercise and diet on CD specifically were mediated by apoptosis. Discussion: Diet and exercise might influence neurogenesis long before the onset of CD and dementia. Alterations in HN could signify the start of the pathological process and potentially represent biomarkers for CD and dementia
Universal contributions to scalar masses from five dimensional supergravity
We compute the effective Kahler potential for matter fields in warped
compactifications, starting from five dimensional gauged supergravity, as a
function of the matter fields localization. We show that truncation to zero
modes is inconsistent and the tree-level exchange of the massive gravitational
multiplet is needed for consistency of the four-dimensional theory. In addition
to the standard Kahler coming from dimensional reduction, we find the quartic
correction coming from integrating out the gravity multiplet. We apply our
result to the computation of scalar masses, by assuming that the SUSY breaking
field is a bulk hypermultiplet. In the limit of extreme opposite localization
of the matter and the spurion fields, we find zero scalar masses, consistent
with sequestering arguments. Surprisingly enough, for all the other cases the
scalar masses are tachyonic. This suggests the holographic interpretation that
a CFT sector always generates operators contributing in a tachyonic way to
scalar masses. Viability of warped su- persymmetric compactifications
necessarily asks then for additional contributions. We discuss the case of
additional bulk vector multiplets with mixed boundary conditions, which is a
partic- ularly simple and attractive way to generate large positive scalar
masses. We show that in this case successful fermion mass matrices implies
highly degenerate scalar masses for the first two generations of squarks and
sleptons.Comment: 23 pages. v2: References added, new section on effect of additional
bulk vector multiplets and phenomenolog
The supermultiplet of boundary conditions in supergravity
Boundary conditions in supergravity on a manifold with boundary relate the
bulk gravitino to the boundary supercurrent, and the normal derivative of the
bulk metric to the boundary energy-momentum tensor. In the 3D N=1 setting, we
show that these boundary conditions can be stated in a manifestly
supersymmetric form. We identify the Extrinsic Curvature Tensor Multiplet, and
show that boundary conditions set it equal to (a conjugate of) the boundary
supercurrent multiplet. Extension of our results to higher-dimensional models
(including the Randall-Sundrum and Horava-Witten scenarios) is discussed.Comment: 22 pages. JHEP format; references added; published versio
A natural little hierarchy for RS from accidental SUSY
We use supersymmetry to address the little hierarchy problem in
Randall-Sundrum models by naturally generating a hierarchy between the IR scale
and the electroweak scale. Supersymmetry is broken on the UV brane which
triggers the stabilization of the warped extra dimension at an IR scale of
order 10 TeV. The Higgs and top quark live near the IR brane whereas light
fermion generations are localized towards the UV brane. Supersymmetry breaking
causes the first two sparticle generations to decouple, thereby avoiding the
supersymmetric flavour and CP problems, while an accidental R-symmetry protects
the gaugino mass. The resulting low-energy sparticle spectrum consists of
stops, gauginos and Higgsinos which are sufficient to stabilize the little
hierarchy between the IR scale and the electroweak scale. Finally, the
supersymmetric little hierarchy problem is ameliorated by introducing a singlet
Higgs field on the IR brane.Comment: 37 pages, 3 figures; v2: minor corrections, version published in JHE
Experimental Probes of the Randall-Sundrum Infinite Extra Dimension
The phenomenological possibilities of the Randall-Sundrum non-compact extra
dimension scenario with the AdS horizon increased to approximately a millimeter
length, corresponding to an effective brane tension of TeV^4, are investigated.
The corrections to the Newtonian potential are found to be the only
observationally accessible probe of this scenario, as previously suggested in
the literature. In particular, the presence of the continuum of KK modes does
not lead to any observable collider signatures. The extent to which
experimental tests of Newtonian gravity can distinguish this scenario from the
scenario of Arkani-Hamed, Dimopoulos, and Dvali with one and two millimeter
size extra dimensions is explicitly demonstrated.Comment: 22 pages, 2 figures, references adde
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