118743945
Solar Neutrino Physics: Sensitivity to Light Dark Matter Particles
Neutrinos are produced in several neutrino nuclear reactions of the proton–proton chain and carbon– nitrogen–oxygen cycle that take place at different radius of the Sun’s core. Hence, measurements of solar neutrino fluxes provide a precise determination of the local temperature. The accumulation of non-annihilating light dark matter particles (with masses between 5 GeV and 16 GeV) in the Sun produces a change in the local solar structure, namely, a decrease in the central temperature of a few percent. This variation depends on the properties of the dark matter particles, such as the mass of the particle and its spin-independent scattering cross-section on baryon-nuclei, specifically, the scattering with helium, oxygen, and nitrogen among other heavy elements. This temperature effect can be measured in almost all solar neutrino fluxes. In particular, by comparing the neutrino fluxes generated by stellar models with current observations, namely 8 B neutrino fluxes, we find that non-annihilating dark matter particles with a mass smaller than 10 GeV and a spin-independent scattering cross-section with heavy baryon-nuclei larger than 3 × 10 −37 cm −2 produce a variation in the 8 B neutrino fluxes that would be in conflict with current measurements.
119176952
How the universe got its spots
The universe displays a three-dimensional pattern of hot and cold spots in the radiation remnant from the big bang. The global geometry of the universe can be revealed in the spatial distribution of these spots. In a topologically compact universe, distinctive patterns are especially prominent in spatial correlations of the radiation temperature. Whereas these patterns are usually washed out in statistical averages, we propose a scheme which uses the universe’s spots to observe global geometry in a manner analogous to the use of multiple images of a gravitationally lensed quasar to study the geometry of the lens. To demonstrate how the geometry of space forms patterns, we develop a simple real-space approximation to estimate temperature correlations for any set of cosmological parameters and any global geometry. We present correlated spheres which clearly show topological pattern formation for compact flat universes as well as for the compact negatively curved space introduced by Weeks and another discovered by Best. These examples illustrate how future satellite-based observations of the microwave background can determine the full geometry of the universe. @S0556-2821~98!02124-9# PACS number~s!: 98.70.Vc, 98.80.Hw From the zebra’s stripes to the leopard’s spots, the animal kingdom displays a diversity of coat patterns. Following the innovative ideas of Turing @1#, mathematical biologists have posed and partly answered the question of how the leopard got its spots. The fluctuation of enzymes diffusing through the developing embryo can lead to the spatial pattern formation displayed by animal coats. Both the geometry and size of the animal exert a strong influence on differentiating patterns. For instance, the broad cylindrical shape of the leopard’s body favors spots while the tapered tail induces stripes @2#. Remarkably, these diverse features can arise from the properties of simple solutions to second-order partial differential equations on the geometry and topology appropriate for animal limbs, tails, or bodies. 1
119106291
Most massive haloes with Gumbel statistics
We present an analytical calculation of the extreme value statistics for dark matter halos - that is, the probability distribution of the most massive halo within some region of the universe of specified shape and size. Our calculation makes use of the counts-in-cells formalism for the correlation functions, and the halo bias derived from the Sheth-Tormen mass function. We demonstrate the power of the method on spherical regions, comparing the results to measurements in a large cosmological dark matter simulation and achieving good agreement. Particularly good fits are obtained for the most likely value of the maximum mass and for the high-mass tail of the distribution, relevant in constraining cosmologies by observations of most massive clusters.
15837031
Reconstruction of primordial density fields
The Monge–Ampere–Kantorovich (MAK) reconstruction is tested against cosmological N-body simulations. Using only the present mass distribution sampled with particles, and the assumption of homogeneity of the primordial distribution, MAK recovers for each particle the non-linear displacement field between its present position and its Lagrangian position on a primordial uniform grid. 
 
 
 
To test the method, we examine a standard Lambda cold dark matter (ΛCDM) N-body simulation with Gaussian initial conditions and six models with non-Gaussian initial conditions: a χ2 model, a model with primordial voids and four weakly non-Gaussian models. 
 
 
 
Our extensive analyses of the Gaussian simulation show that the level of accuracy of the reconstruction of the non-linear displacement field achieved by MAK is unprecedented, at scales as small as ∼3 h−1 Mpc. In particular, it captures in a non-trivial way the non-linear contribution from gravitational instability, well beyond the Zel'dovich approximation. This is also confirmed by our analyses of the non-Gaussian samples. 
 
 
 
Applying the spherical collapse model to the probability distribution function of the divergence of the displacement field, we also show that from a well-reconstructed displacement field, such as that given by MAK, it is possible to accurately disentangle dynamical contributions induced by gravitational clustering from possible initial non-Gaussianities, allowing one to efficiently test the non-Gaussian nature of the primordial fluctuations. 
 
 
 
In addition, we test successfully a simple application of MAK using the Zel'dovich approximation to recover in real space the present-day peculiar velocity field on scales of 8 h−1 Mpc. 
 
 
 
Although non-trivial observational issues yet remain to be addressed, our numerical investigations suggest that MAK reconstruction represents a very promising tool to be applied to three-dimensional Galaxy catalogues.
119050418
Neutrinos from dark matter annihilations at the galactic center
We discuss the prospects for detection of high energy neutrinos from dark matter annihilation at the Galactic centre. Despite the large uncertainties associated with our poor knowledge of the distribution of dark matter in the innermost regions of the Galaxy, we determine an upper limit on the neutrino flux by requiring that the associated gamma-ray emission does not exceed the observed flux. We conclude that if dark matter is made of neutralinos, a neutrino flux from dark matter annihilations at the GC will not be observable by Antares. Conversely, the positive detection of such a flux would either require an alternative explanation, in terms of astrophysical processes, or the adoption of other \DM candidates, disfavouring the case for neutralinos.
15995519
How flat can you get? A model comparison perspective on the curvature of the Universe
The question of determining the spatial geometry of the Universe is of greater relevance than ever, as precision cosmology promises to verify inflationary predictions about the curvature of the Universe. We revisit the question of what can be learnt about the spatial geometry of the Universe from the perspective of a three-way Bayesian model comparison. By considering two classes of phenomenological priors for the curvature parameter, we show that, given the current data, the probability that the Universe is spatially infinite lies between 67 and 98 per cent, depending on the choice of priors. For the strongest prior choice, we find odds of the order of 50:1 (200:1 ) in favour of a flat Universe when compared with a closed (open) model. We also report a robust, prior-independent lower limit to the number of Hubble spheres in the Universe, N U ≥ 5 (at 99 per cent confidence). We forecast the accuracy with which future cosmic microwave background (CMB) and baryonic acoustic oscillation (BAO) observations will be able to constrain curvature, finding that a cosmic variance-limited CMB experiment together with an Square Kilometer Array (SKA)-like BAO observation will constrain curvature independently of the equation of state of dark energy with a precision of about σ ∼ 4.5 x 10 ―4 . We demonstrate that the risk of 'model confusion' (i.e. wrongly favouring a flat Universe in the presence of curvature) is much larger than might be assumed from parameter error forecasts for future probes. We argue that a 5σ detection threshold guarantees a confusion- and ambiguity-free model selection. Together with inflationary arguments, this implies that the geometry of the Universe is not knowable if the value of the curvature parameter is below |Ω κ | ∼ 10- 4 . This bound is one order of magnitude larger than what one would naively expect from the size of curvature perturbations, ∼10 ―5 .
125435973
Reaction Ni-58 (pi+, p p) at T(pi+) = 160-MeV
124311895
Evaluation of correlation functions in integrable quantum field theories
The aim of this thesis is to explore correlation functions in two dimensional quantum field theories in two distinct ways. In part I a new method for calculating the differential equations parametrising the correlation functions of twist fields associated with the U (1) symmetry of the Dirac model is presented. While developing this method a new family of descendent twist fields are identified and their form factors calculated. This provides a novel way of calculating the vacuum expectation values of the primary twist fields and is shown to be entirely consistent with known results. The method of calculating the correlation functions of twist fields provides a parametrisation of several other correlation functions for various quantum states. Since this method relies on the Ward identities found in a double copy model it is hoped to have wider applications in other free fermion models. Part II concerns the truncated conformal space approach which has been developed to approximate perturbed conformal field theories. In this part the theory underpinning the approach is discussed and a working algorithm is developed for both bulk and boundary perturbed minimal models. The energy levels, mass gaps and one point functions of various models are computed using the truncated conformal space approach and are shown to be in good agreement with previous calculations. A possible method for using this approach to approximate two point functions in perturbed conformal field theories is discussed.
122618150
Energy dissipation process for 100-MeV protons and the nucleon-nucleon interactions in nuclei
Coincidence studies of two protons emitted from p+/sup 58/Ni at 100 MeV have been carried out. The proton spectra in coincidence with scattered protons suffering an average energy loss of 60 MeV are similar to those resulting from 60-MeV incident protons. This suggests that the initial interaction of the incident proton is with a bound nucleon and that one or both of these nucleons are emitted or initiates a cascade leading to more complex states.
119291656
Correlation functions of twist fields from Ward identities in the massive Dirac theory
We derive non-linear differential equations for correlation functions of U(1) twist fields in the two-dimensional massive Dirac theory. Primary U(1) twist fields correspond to exponential fields in the sine-Gordon model at the free-fermion point, and it is well-known that their vacuum two-point functions are determined by integrable differential equations. We extend part of this result to more general quantum states (pure or mixed) and to certain descendents, showing that some two-point functions are determined by the sinh-Gordon differential equations whenever there is translation and parity invariance, and the density matrix is the exponential of a bilinear expression in fermions. We use methods involving Ward identities associated to the copy-rotation symmetry in a model with two independent, anti-commuting copies. Such methods were used in the context of the thermally perturbed Ising quantum field theory model. We show that they are applicable to the Dirac theory as well, and we suggest that they are likely to have a much wider applicability to free fermion models in general. Finally, we note that our form-factor study of descendents twist fields combined with a CFT analysis provides a new way of evaluating vacuum expectation values of primary U(1) twist fields: by deriving and solving a recursion relation.