4,964 research outputs found
A Precision Search for WIMPs with Charged Cosmic Rays
AMS-02 has reached the sensitivity to probe canonical thermal WIMPs by their
annihilation into antiprotons. Due to the high precision of the data,
uncertainties in the astrophysical background have become the most limiting
factor for indirect dark matter detection. In this work we systematically
quantify and -- where possible -- reduce uncertainties in the antiproton
background. We constrain the propagation of charged cosmic rays through the
combination of antiproton, B/C and positron data. Cross section uncertainties
are determined from a wide collection of accelerator data and are -- for the
first time ever -- fully taken into account. This allows us to robustly
constrain even subdominant dark matter signals through their spectral
properties. For a standard NFW dark matter profile we are able to exclude
thermal WIMPs with masses up to 570 GeV which annihilate into bottom quarks.
While we confirm a reported excess compatible with dark matter of mass around
80 GeV, its local (global) significance only reaches 2.2 sigma (1.1 sigma) in
our analysis.Comment: 38 pages + references, 14 figure
The Cosmic Ray Antiproton Background for AMS-02
The AMS-02 experiment is measuring the cosmic ray antiproton flux with high
precision. The interpretation of the upcoming data requires a thorough
understanding of the secondary antiproton background. In this work, we employ
newly available data of the NA49 experiment at CERN, in order to recalculate
the antiproton source term arising from cosmic ray spallations on the
interstellar matter. We systematically account for the production of
antiprotons via hyperon decay and discuss the possible impact of isospin
effects on antineutron production. A detailed comparison of our calculation
with the existing literature as well as with Monte Carlo based evaluations of
the antiproton source term is provided. Our most important result is an updated
prediction for the secondary antiproton flux which includes a realistic
assessment of the particle physics uncertainties at all energies.Comment: 24 pages, 10 figures, source term and secondary flux available in the
ancillary file
Inflation with Fayet-Iliopoulos Terms
Two of the most attractive realizations of inflation in supergravity are
based upon the presence of a constant Fayet-Iliopoulos (FI) term. In D-term
hybrid inflation it is the FI term itself which sets the energy scale of
inflation. Alternatively, the breaking of a U(1) symmetry induced by the FI
term can dynamically generate the quadratic potential of chaotic inflation. The
purpose of this note is to study the possible UV embedding of these schemes in
terms of the `field-dependent FI term' related to a string modulus field which
is stabilized by a non-perturbative superpotential. We find that in settings
where the FI term drives inflation, gauge invariance prevents a decoupling of
the modulus from the inflationary dynamics. The resulting inflation models
generically contain additional dynamical degrees of freedom compared to D-term
hybrid inflation. However, the dynamical realization of chaotic inflation can
be obtained in complete analogy to the case of a constant FI term. We present a
simple string-inspired toy model of this type.Comment: 20 pages, accepted for publication in PR
The trade-off characteristics of acoustic and pressure sensors for the NASP
Results of a trade study for the development of pressure and acoustic sensors for use on the National Aerospace Plane (NASP) are summarized. Pressure sensors are needed to operate to 100 psia; acoustic sensors are needed that can give meaningful information about a 200 dB sound pressure level (SPL) environment. Both sensors will have to operate from a high temperature of 2000 F down to absolute zero. The main conclusions of the study are the following: (1) Diaphragm materials limit minimum size and maximum frequency response attainable. (2) No transduction is available to meet all the NASP requirements with existing technology. (3) Capacitive sensors are large relative to the requirement, have limited resolution and frequency response due to noise, and cable length is limited to approximately 20 feet. (4) Eddy current sensors are large relative to the requirement and have limited cable lengths. (5) Fiber optic sensors provide the possibility for a small sensor, even though present developments do not exhibit that characteristic. The need to use sapphire at high temperature complicates the design. Present high temperature research sensors suffer from poor resolution. A significant development effort will be required to realize the potential of fiber optics. (6) Short-term development seems to favor eddy current techniques with the penalty of larger size and reduced dynamic range for acoustic sensors. (7) Long-term development may favor fiber optics with the penalties of cost, schedule, and uncertainty
Further Baire results on the distribution of subsequences
This paper presents results about the distribution of subsequences which are
typical in the sense of Baire.
The first part is concerned with sequences of the type x_k = n_k*alpha, n_1 <
n_2 < n_3 < ..., mod 1. Improving a result of Salat we show that, if the
quotients q_k = n_{k+1}/n_k satisfy q_k > 1+ epsilon, then the set of alpha
such that (x_k) is uniformly distributed is of first Baire category, i.e. for
generic alpha we do not have uniform distribution. Under the stronger
assumption lim q_k = infinity one even has maldistribution for generic alpha,
the strongest possible contrast to uniform distribution.
The second part reverses the point of view by considering appropriately
defined Baire spaces S of subsequences. For a fixed well distributed sequence
(x_n) we show that there is a set M of measures such that for generic (n_k) in
S the set of limit measures of the subsequence (x_{n_k}) is exactly M.Comment: 21 pages, LaTeX2e. Final version. (Somewhat expanded proofs and
clarifications, more examples
Supersymmetric Moduli Stabilization and High-Scale Inflation
We study the back-reaction of moduli fields on the inflaton potential in
generic models of F-term inflation. We derive the moduli corrections as a power
series in the ratio of Hubble scale and modulus mass. The general result is
illustrated with two examples, hybrid inflation and chaotic inflation. We find
that in both cases the decoupling of moduli dynamics and inflation requires
moduli masses close to the scale of grand unification. For smaller moduli
masses the CMB observables are strongly affected.Comment: 5 page
Natural Inflation and Low Energy Supersymmetry
Natural (axionic) inflation provides a well-motivated and predictive scheme
for the description of the early universe. It leads to sizeable primordial
tensor modes and thus a high mass scale of the inflationary potential. Naively
this seems to be at odds with low (TeV) scale supersymmetry, especially when
embedded in superstring theory. We show that low scale supersymmetry is
compatible with natural (high scale) inflation. The mechanism requires the
presence of two axions that are provided through the moduli of string theory.Comment: 15 pages, 4 figure
Modulated Natural Inflation
We discuss some model-independent implications of embedding (aligned) axionic
inflation in string theory. As a consequence of string theoretic duality
symmetries the pure cosine potentials of natural inflation are replaced by
modular functions. This leads to "wiggles" in the inflationary potential that
modify the predictions with respect to CMB-observations. In particular, the
scalar power spectrum deviates from the standard power law form. As a
by-product one can show that trans-Planckian excursions of the aligned
effective axion are compatible with the weak gravity conjecture.Comment: 8 pages, 6 figure
UV Corrections in Sgoldstino-less Inflation
We study the embedding of inflation with nilpotent multiplets in
supergravity, in particular the decoupling of the sgoldstino scalar field.
Instead of being imposed by hand, the nilpotency constraint on the goldstino
multiplet arises in the low energy-effective theory by integrating out heavy
degrees of freedom. We present explicit supergravity models in which a large
but finite sgoldstino mass arises from Yukawa or gauge interactions. In both
cases the inflaton potential receives two types of corrections. One is from the
backreaction of the sgoldstino, the other from the heavy fields generating its
mass. We show that these scale oppositely with the Volkov-Akulov cut-off scale,
which makes a consistent decoupling of the sgoldstino nontrivial. Still, we
identify a parameter window in which sgoldstino-less inflation can take place,
up to corrections which flatten the inflaton potential.Comment: 7 pages, 1 figure. Comments added, published versio
- …