573 research outputs found
Distributed SUSY Breaking: Dark Energy, Newton's Law and the LHC
We identify the underlying symmetry mechanism that suppresses the low-energy
effective 4D cosmological constant within 6D supergravity models, leading to
results suppressed by powers of the KK scale relative to the much larger masses
associated with particles localized on codimension-2 branes. In these models
the conditions for unbroken supersymmetry can be satisfied locally everywhere
within the extra dimensions, but are obstructed by global conditions like flux
quantization or the mutual inconsistency of boundary conditions at the various
branes. Consequently quantities forbidden by supersymmetry cannot be nonzero
until wavelengths of order the KK scale are integrated out, since only such
long wavelength modes see the entire space and so know that supersymmetry
breaks. We verify these arguments by extending earlier rugby-ball calculations
of one-loop vacuum energies to more general pairs of branes within two warped
extra dimensions. The predicted effective 4D vacuum energy density can be of
order C (m Mg/4 pi Mp)^4, where Mg (Mp) is the rationalized 6D (4D) Planck
scale and m is the heaviest brane-localized particle. Numerically this is C
(5.6 x 10^{-5} eV)^4 if we take m = 173 GeV and take Mg as small as possible
(10 TeV corresponding to KK size r < 1 micron), consistent with supernova
bounds. C is a constant depending on details of the bulk spectrum, which could
be ~ 500 for each of hundreds of fields. The value C ~ 6 x 10^6 gives the
observed Dark Energy density
Gravitational Forces on a Codimension-2 Brane
We compute the gravitational response of six dimensional gauged, chiral
supergravity to localized stress energy on one of two space-filling branes,
including the effects of compactifying the extra dimensions and brane
back-reaction. We find a broad class of exact solutions, including various
black-brane solutions. Several approximate solutions are also described, such
as the near-horizon geometry of a small black hole which is argued to be
approximately described by a 6D Schwarzschild (or Kerr) black hole, with event
horizon appropriately modified to encode the brane back-reaction. The general
linearized far-field solutions are found in the 4D regime very far from the
source, and all integration constants are related to physical quantities
describing the branes and the localized energy source. The localized source
determines two of these, corresponding to the source mass and the size of the
strength of a coupling to a 4D scalar mode whose mass is parametrically smaller
than the KK scale. At large distances the solutions agree with those of 4D
general relativity, but for an intermediate range of distances (larger than the
KK scale) the solutions better fit a Brans-Dicke theory. For a realistic choice
of parameters the KK scale could lie at a micron, while the crossover to
Brans-Dicke behaviour could occur at around 10 microns. While allowed by
present data this points to potentially measurable changes to Newton's Law
arising at distances larger than the KK scale.Comment: 31 pages + appendices, 2 figure
Running with Rugby Balls: Bulk Renormalization of Codimension-2 Branes
We compute how one-loop bulk effects renormalize both bulk and brane
effective interactions for geometries sourced by codimension-two branes. We do
so by explicitly integrating out spin-zero, -half and -one particles in
6-dimensional Einstein-Maxwell-Scalar theories compactified to 4 dimensions on
a flux-stabilized 2D geometry. (Our methods apply equally well for D dimensions
compactified to D-2 dimensions, although our explicit formulae do not capture
all divergences when D>6.) The renormalization of bulk interactions are
independent of the boundary conditions assumed at the brane locations, and
reproduce standard heat-kernel calculations. Boundary conditions at any
particular brane do affect how bulk loops renormalize this brane's effective
action, but not the renormalization of other distant branes. Although we
explicitly compute our loops using a rugby ball geometry, because we follow
only UV effects our results apply more generally to any geometry containing
codimension-two sources with conical singularities. Our results have a variety
of uses, including calculating the UV sensitivity of one-loop vacuum energy
seen by observers localized on the brane. We show how these one-loop effects
combine in a surprising way with bulk back-reaction to give the complete
low-energy effective cosmological constant, and comment on the relevance of
this calculation to proposed applications of codimension-two 6D models to
solutions of the hierarchy and cosmological constant problems.Comment: 42 pages + appendices. This is the final version which appears in
JHE
Accidental SUSY: Enhanced Bulk Supersymmetry from Brane Back-reaction
We compute how bulk loops renormalize both bulk and brane effective
interactions for codimension-two branes in 6D gauged chiral supergravity, as
functions of the brane tension and brane-localized flux. We do so by explicitly
integrating out hyper- and gauge-multiplets in 6D gauged chiral supergravity
compactified to 4D on a flux-stabilized 2D rugby-ball geometry, specializing
the results of a companion paper, arXiv:1210.3753, to the supersymmetric case.
While the brane back-reaction generically breaks supersymmetry, we show that
the bulk supersymmetry can be preserved if the amount of brane-localized flux
is related in a specific BPS-like way to the brane tension, and verify that the
loop corrections to the brane curvature vanish in this special case. In these
systems it is the brane-bulk couplings that fix the size of the extra
dimensions, and we show that in some circumstances the bulk geometry
dynamically adjusts to ensure the supersymmetric BPS-like condition is
automatically satisfied. We investigate the robustness of this residual
supersymmetry to loops of non-supersymmetric matter on the branes, and show
that supersymmetry-breaking effects can enter only through effective brane-bulk
interactions involving at least two derivatives. We comment on the relevance of
this calculation to proposed applications of codimension-two 6D models to
solutions of the hierarchy and cosmological constant problems.Comment: 49 pages + appendices. This is the final version to appear in JHE
Consideration sets, intentions and the inclusion of "Don't know" in a two-stage model for voter choice
We present a statistical model for voter choice that incorporates a consideration set stage and final vote intention stage. The first stageinvolves a multivariate probit model for the vector of probabilities that a candidate or a party gets considered. The second stage of the model is a multinomial probit model for the actual choice. In both stages we use asexplanatory variables data on voter choice at the previous election, as well as socio-demographic respondent characteristics. Importantly, our modelexplicitly accounts for the three types of "missing data" encountered in polling. First, we include a no-vote option in the final vote intention stage. Second, the "do not know" response is assumed to arise from too little difference in the utility between the two most preferred options in the consideration set. Third, the "do not want to say" response is modelled as a missing observation on the most preferred alternative in the consideration set. Thus, we consider the missing data generating mechanism to be non-ignorable and build a model based on utility maximization to describe the voting intentions of these respondents. We illustrate the merits of the model as we have information on a sample of about 5000 individuals from the Netherlands for who we know how they voted last time (if at all), which parties they would consider for the upcoming election,and what their voting intention is. A unique feature of the data set is that information is available on actual individual voting behavior, measured at the day of election. We find that the inclusion of the consideration set stage in the model enables the user to make more precise inferences on the competitive structure in the political domain and to get better out-of-sample forecasts.Bayesian method;Choice model;Election data;Polling;Probit model
Effects of organically and conventionally produced feed on biomarkers of health in a chicken model
Consumers expect organic products to be healthier. However, limited research has been performed to study the effect of organic food on health. The present study aimed to identify biomarkers of health to enable future studies in human subjects. A feeding experiment was performed in two generations of three groups of chickens differing in immune responsiveness, which were fed identically composed feeds from either organic or conventional produce. The animals of the second generation were exposed to an immune challenge and sacrificed at 13 weeks of age. Feed and ingredients were analysed on macro- and micronutrients, i.e. vitamins, minerals, trace elements, heavy metals and microbes. The chickens were studied by general health and immune parameters, metabolomics, genomics and post-mortem evaluation. The organic and conventional feeds were comparable with respect to metabolisable energy. On average, the conventionally produced feeds had a 10 % higher protein content and some differences in micronutrients were observed. Although animals on both feeds were healthy, differences between the groups were found. The random control group of chickens fed conventional feed showed overall a higher weight gain during life span than the group on organic feed, although feed intake was mostly comparable. The animals on organic feed showed an enhanced immune reactivity, a stronger reaction to the immune challenge as well as a slightly stronger ‘catch-up growth’ after the challenge. Biomarkers for future research were identified in the parameters feed intake, body weight and growth rate, and in immunological, physiological and metabolic parameters, several of these differing most pronounced after the challeng
Retrieving unobserved consideration sets from household panel data
We propose a new model to describe consideration, consisting of a multivariate
probit model component for consideration and a multinomial probit model
component for choice, given consideration. The approach allows one to analyze
stated consideration set data, revealed consideration set (choice) data or
both, while at the same time it allows for unobserved dependence in
consideration among brands. In addition, the model accommodates different
effects of the marketing mix on consideration and choice, an error process that
is correlated over time, and unobserved consumer heterogeneity in both processes.
We attempt to establish the validity of existing practice to infer
consideration sets from observed choices in panel data. To this end, we collect
data in an on-line choice experiment involving interactive supermarket shelves
and post-choice questionnaires to measure the choice protocol and stated
consideration levels. We show with these experimental data that underlying
consideration sets can be reliably retrieved from choice data alone.
Next, we estimate the model on IRI panel data. We have two main results. First,
compared with the single-stage multinomial probit model, promotion effects are
larger when they are included in the consideration stage of the two-stage
model. Second, we find that consideration of brands does not covary greatly
across brands once we account for observed effects
Consideration sets, intentions and the inclusion of "Don't know" in a two-stage model for voter choice
We present a statistical model for voter choice that incorporates a consideration set stage and final vote intention stage. The first stage
involves a multivariate probit model for the vector of probabilities that a candidate or a party gets considered. The second stage of the model is a multinomial probit model for the actual choice. In both stages we use as
explanatory variables data on voter choice at the previous election, as well as socio-demographic respondent characteristics. Importantly, our model
explicitly accounts for the three types of "missing data" encountered in polling. First, we include a no-vote option in the final vote intention stage. Second, the "do not know" response is assumed to arise from too little difference in the utility between the two most preferred options in the consideration set. Third, the "do not want to say" response is modelled as a missing observation on the most preferred alternative in the consideration set. Thus, we consider the missing data generating mechanism to be non-ignorable and build a model based on utility maximization to describe the voting intentions of these respondents. We illustrate the merits of the model as we have information on a sample of about 5000 individuals from the Netherlands for who we know how they voted last time (if at all), which parties they would consider for the upcoming election,
and what their voting intention is. A unique feature of the data set is that in
Тактика лечения эректильной дисфункции у мужчин без партнерши
Обосновывается актуальность проблемы оказания помощи мужчинам с эректильной дисфункцией, не имеющим сексуальной партнерши. Описаны предложенные автором подходы к коррекции нарушения сексуального здоровья мужчин и лечебные тактики.The importance of the issue of rendering the aid to the men with erectile dysfunction who do not have a female partner is substantiated. The author describes the original approaches to correction of the sexual health in the men and therapeutic tactics
Elevated EBNA-1 IgG in MS is associated with genetic MS risk variants
Objective: To assess whether MS genetic risk polymorphisms (single nucleotide polymorphism [SNP]) contribute to the enhanced humoral immune response against Epstein-Barr virus (EBV) infection in patients with MS. Methods: Serum anti-EBV nuclear antigen 1 (EBNA-1) and early antigen D (EA-D) immunoglobulin γ (IgG) levels were quantitatively determined in 668 genotyped patients with MS and 147 healthy controls. Anti-varicella-zoster virus (VZV) IgG levels were used as a highly prevalent, non-MS-Associated control herpesvirus. Associations between virus-specific IgG levels and MS risk SNPs were analyzed. Results: IgG levels of EBNA-1, but not EA-D and VZV, were increased in patients with MS compared with healthy controls. Increased EBNA-1 IgG levels were significantly associated with risk alleles of SNP rs2744148 (SOX8), rs11154801 (MYB), rs1843938 (CARD11), and rs7200786 (CLEC16A/CIITA) in an interaction model and a trend toward significance for rs3135388 (HLA-DRB1-1501). In addition, risk alleles of rs694739 (PRDX5/BAD) and rs11581062 (VCAM1) were independently associated and interacted with normal EBNA-1 IgG levels. None of these interactions were associated with EA-D and VZV IgG titers. Conclusions: Several MS-Associated SNPs significantly correlated with differential IgG levels directed to a latent, but not a lytic EBV protein. The data suggest that the aforementioned immune-related genes orchestrate the aberrant EBNA-1 IgG levels
- …