1,050 research outputs found
What can(not) be measured with ton-scale dark matter direct detection experiments
Direct searches for dark matter have prompted in recent years a great deal of
excitement within the astroparticle physics community, but the compatibility
between signal claims and null results of different experiments is far from
being a settled issue. In this context, we study here the prospects for
constraining the dark matter parameter space with the next generation of
ton-scale detectors. Using realistic experimental capabilities for a wide range
of targets (including fluorine, sodium, argon, germanium, iodine and xenon),
the role of target complementarity is analysed in detail while including the
impact of astrophysical uncertainties in a self-consistent manner. We show
explicitly that a multi-target signal in future direct detection facilities can
determine the sign of the ratio of scalar couplings , but not its
scale. This implies that the scalar-proton cross-section is left essentially
unconstrained if the assumption is relaxed. Instead, we find that
both the axial-proton cross-section and the ratio of axial couplings
can be measured with fair accuracy if multi-ton instruments using sodium and
iodine will eventually come online. Moreover, it turns out that future direct
detection data can easily discriminate between elastic and inelastic
scatterings. Finally, we argue that, with weak assumptions regarding the WIMP
couplings and the astrophysics, only the dark matter mass and the inelastic
parameter (i.e. mass splitting) may be inferred from the recoil spectra --
specifically, we anticipate an accuracy of tens of GeV (tens of keV) in the
measurement of the dark matter mass (inelastic parameter).Comment: 31 pages, 7 figures, 7 table
The Spectral Action Principle in Noncommutative Geometry and the Superstring
A supersymmetric theory in two-dimensions has enough data to define a
noncommutative space thus making it possible to use all tools of noncommutative
geometry. In particular, we apply this to the N=1 supersymmetric non-linear
sigma model and derive an expression for the generalized loop space Dirac
operator, in presence of a general background, using canonical quantization.
The spectral action principle is then used to determine a spectral action valid
for the fluctuations of the string modes.Comment: Latex file, 13 pages. Correction to equation 47, which should read
Tr| |^2 and not |Tr |^2. Final form to appear in Physics Letters
Conditions for Successful Extended Inflation
We investigate, in a model-independent way, the conditions required to obtain
a satisfactory model of extended inflation in which inflation is brought to an
end by a first-order phase transition. The constraints are that the correct
present strength of the gravitational coupling is obtained, that the present
theory of gravity is satisfactorily close to general relativity, that the
perturbation spectra from inflation are compatible with large scale structure
observations and that the bubble spectrum produced at the phase transition
doesn't conflict with the observed level of microwave background anisotropies.
We demonstrate that these constraints can be summarized in terms of the
behaviour in the conformally related Einstein frame, and can be compactly
illustrated graphically. We confirm the failure of existing models including
the original extended inflation model, and construct models, albeit rather
contrived ones, which satisfy all existing constraints.Comment: 8 pages RevTeX file with one figure incorporated (uses RevTeX and
epsf). Also available by e-mailing ARL, or by WWW at
http://star-www.maps.susx.ac.uk/papers/infcos_papers.html; Revised to include
extra references, results unchanged, to appear Phys Rev
Models of Dynamical Supersymmetry Breaking with Gauged Symmetry
We present simple models of dynamical supersymmetry breaking with gauged
U(1)_R symmetry. The minimal supersymmetric standard model and supersymmetric
SU(5) GUT are considered as the visible sector. The anomaly cancellation
conditions for U(1)_R are investigated in detail and simple solutions of the
R-charge assignments are found. We show that this scenario of dynamical
supersymmetry breaking is phenomenologically viable with the gravitino mass of
order 1 TeV or 10 TeV.Comment: 15 pages, uses REVTEX macro, No figure
Pure type I supergravity and DE(10)
We establish a dynamical equivalence between the bosonic part of pure type I
supergravity in D=10 and a D=1 non-linear sigma-model on the Kac-Moody coset
space DE(10)/K(DE(10)) if both theories are suitably truncated. To this end we
make use of a decomposition of DE(10) under its regular SO(9,9) subgroup. Our
analysis also deals partly with the fermionic fields of the supergravity theory
and we define corresponding representations of the generalized spatial Lorentz
group K(DE(10)).Comment: 28 page
Anomaly-Free Gauged R-Symmetry in Local Supersymmetry
We discuss local \R-symmetry as a potentially powerful new model building
tool. We first review and clarify that a \R-symmetry can only be gauged
in local and not in global supersymmetry. We determine the anomaly-cancellation
conditions for the gauged \R-symmetry. For the standard superpotential these
equations have {\it no} solution, independently of how many Standard Model
singlets are added to the model. There is also no solution when we increase the
number of families and the number of pairs of Higgs doublets. When the
Green-Schwarz mechanism is employed to cancel the anomalies, solutions only
exist for a large number of singlets. We find many anomaly-free
family-independent models with an extra octet chiral superfield. We
consider in detail the conditions for an anomaly-free {\it family dependent} and find solutions with one, two, three and four extra singlets. Only
with three and four extra singlets do we naturally obtain sfermion masses of
order the weak-scale. For these solutions we consider the spontaneous breaking
of supersymmetry and the -symmetry in the context of local supersymmetry. In
general the gauge group is broken at or close to the Planck scale. We
consider the effects of the \R-symmetry on baryon- and lepton-number violation
in supersymmetry. There is no logical connection between a conserved
\R-symmetry and conserved \R-parity. For conserved \R-symmetry we have models
for all possibilities of conserved or broken \R-parity. Most models predict
dominant effects which could be observed at HERA.Comment: 29 pages, latex, including 3 tables. Final version accepted for
publication in NPB. Slight revision of supersymmetry breaking and dropped
sub-section on mu problem, which will appear expaned elsewher
Combinatorial Markov chains on linear extensions
We consider generalizations of Schuetzenberger's promotion operator on the
set L of linear extensions of a finite poset of size n. This gives rise to a
strongly connected graph on L. By assigning weights to the edges of the graph
in two different ways, we study two Markov chains, both of which are
irreducible. The stationary state of one gives rise to the uniform
distribution, whereas the weights of the stationary state of the other has a
nice product formula. This generalizes results by Hendricks on the Tsetlin
library, which corresponds to the case when the poset is the anti-chain and
hence L=S_n is the full symmetric group. We also provide explicit eigenvalues
of the transition matrix in general when the poset is a rooted forest. This is
shown by proving that the associated monoid is R-trivial and then using
Steinberg's extension of Brown's theory for Markov chains on left regular bands
to R-trivial monoids.Comment: 35 pages, more examples of promotion, rephrased the main theorems in
terms of discrete time Markov chain
Some polynomial solutions for the non-axisymmetric Boussinesq problem
Solutions to the Boussinesq problem for the circular punch without axial symmetry can be obtained from corresponding axisymmetric solutions by parametric differentiation. The method is applied to the problem of the tilted flat punch, originally solved by Green, and to the indentation of a cylindrical surface by a flat circular punch.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42671/1/10659_2004_Article_BF00041668.pd
Bianchi type I space and the stability of inflationary Friedmann-Robertson-Walker space
Stability analysis of the Bianchi type I universe in pure gravity theory is
studied in details. We first derive the non-redundant field equation of the
system by introducing the generalized Bianchi type I metric. This non-redundant
equation reduces to the Friedmann equation in the isotropic limit. It is shown
further that any unstable mode of the isotropic perturbation with respect to a
de Sitter background is also unstable with respect to anisotropic
perturbations. Implications to the choice of physical theories are discussed in
details in this paper.Comment: 5 pages, some comment adde
Friedmann Equation and Stability of Inflationary Higher Derivative Gravity
Stability analysis on the De Sitter universe in pure gravity theory is known
to be useful in many aspects. We first show how to complete the proof of an
earlier argument based on a redundant field equation. It is shown further that
the stability condition applies to Friedmann-Robertson-Walker spaces
based on the non-redundant Friedmann equation derived from a simple effective
Lagrangian. We show how to derive this expression for the Friedmann equation of
pure gravity theory. This expression is also generalized to include scalar
field interactions.Comment: Revtex, 6 pages, Add two more references, some typos correcte
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