* Astronomy

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RE: Dark matter

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Title: Directional detection of Dark Matter
Authors: F. Mayet (1), J. Billard (1), D. Santos (1) ((1) LPSC Grenoble)

Directional detection is a promising Dark Matter search strategy. Taking advantage on the rotation of the Solar system around the galactic center through the Dark Matter halo, it allows to show a direction dependence of WIMP events. It requires the simultaneous measurement of the energy and the 3D track of low energy recoils, which is a common challenge for all current projects of directional detectors. The third CYGNUS workshop on directional dark matter detection has brought together the scientific community working on both theoretical and experimental aspects of the subject. In this paper, we give an introductory revue of directional detection of Dark Matter, focusing on the main recent progresses.

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Title: Exclusion, Discovery and Identification of Dark Matter with Directional Detection
Authors: J. Billard (1), F. Mayet (1), D. Santos (1) ((1) LPSC Grenoble)

Directional detection is a promising search strategy to discover galactic Dark Matter. We present a Bayesian analysis framework dedicated to data from upcoming directional detectors. The interest of directional detection as a powerful tool to set exclusion limits, to authentify a Dark Matter detection or to constrain the Dark Matter properties, both from particle physics and galactic halo physics, will be demonstrated.

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Title: Dark Matter implications of the Fermi-LAT measurement of anisotropies in the diffuse gamma-ray background: status report
Authors: Mattia Fornasa (1,2), Jesus Zavala (3), Miguel A. Sanchez-Conde (4), Francisco Prada (1), Mark Vogelsberger (5) ((1) Instituto de Astrofisica de Andalucia IAA-CSIC, (2) MultiDark fellow, (3) Department of Physics and Astrophysics, University of Waterloo, (4) KIPAC - SLAC National Accelerator Laboratory, (5) Harvard-Smithsonian Centre for Astrophysics)

For the first time, the Fermi-LAT measured the angular power spectrum (APS) of anisotropies in the diffuse gamma-ray background. The data is found to be broadly compatible with a model with contributions from the point sources in the 1-year catalogue, the galactic diffuse background, and the extragalactic isotropic emission; however deviations are present at both large and small angular scales. In this study, we complement the model with a contribution from Dark Matter (DM) whose distribution is modelled exploiting the results of the most recent N-body simulations, considering the contribution of extragalactic halos and subhalos (from Millennium-II) and of galactic substructures (from Aquarius). With the use of the Fermi Science Tools, these simulations serve as templates to produce mock gamma-ray count maps for DM gamma-ray emission, both in the case of an annihilating and a decaying DM candidate. The APS will then be computed and compared with the Fermi-LAT results to derive constraints on the DM particle physics properties. The possible systematic due to an imperfect model of the galactic foreground is also studied and taken into account properly. The present paper reports on the status of the project.

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Title: Dark Matter in Universe as the Geometry of Empty Space
Authors: Arkady Z. Dolginov

The observed excess of gravitational forces in galaxies and galactic clusters is usually referred as the existence of "dark matter particles" of unknown origin. An alternative explanation of the dark matter effect is presented here by assuming that the empty space of the Universe has a complicated geometrical structure. It is assumed that the cosmological Lambda term, which is approximately constant at scales of several Mpc and describes the dark energy, is not constant at scales of several tenth of Kpc and describes the "dark matter effect". This term is mathematically analogous, but not identical, with the energy-momentum tensor of particles ensembles. In this connection the general expression of the Riemann tensor, which depends on the matter distribution in space and on the empty space geometry, is considered. The Ricci tensor does not describe all possible empty space structures. The tensor of the spin curvature also has to be taken into account. Local deviations of the empty space geometry of Universe from a flat one provide the same observational effect as clouds of invisible particles which demonstrate themselves by their gravitational fields only. The matter, which forms stars and galaxies, will concentrate in gravitational depressions of empty space. The gravitation provides correlation of the luminous matter distribution and geometrical structures of space. The presented theory is compared with observations.

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Title: Astrophysical Constraints on Dark Matter
Authors: Charling Tao

Astrophysics gives evidence for the existence of Dark Matter and puts constraints on its nature. The Cold Dark Matter model has become "standard" cosmology combined with a cosmological constant. There are indications that "Cold" Dark Matter could be "warmer" than initially discussed. This paper reviews the main information on the Cold/Warm nature of Dark Matter.

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Title: Dark Matter Jets at the LHC
Authors: Yang Bai, Arvind Rajaraman

We argue that dark matter particles which have strong interactions with the Standard Model particles are not excluded by current astrophysical constraints. These dark matter particles have unique signatures at colliders; instead of missing energy, the dark matter particles produce jets. We propose a new search strategy for such strongly interacting particles by looking for a signal of two trackless jets. We show that suitable cuts can plausibly allow us to find these signals at the LHC even in early data.

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Title: Ruling Out Bosonic Repulsive Dark Matter
Authors: Zachary Slepian, Jeremy Goodman

Self-interacting dark matter (SIDM), especially bosonic, has been considered a promising candidate to replace cold dark matter (CDM) as it resolves some of the problems associated with CDM. Here, we rule out the possibility that dark matter is a repulsive boson in thermal equilibrium. We develop the model first proposed by Goodman (2000) and derive the equation of state at finite temperature. Isothermal spherical halo models indicate a Bose-Einstein condensed core surrounded by a non-degenerate envelope, with an abrupt density drop marking the boundary between the two phases. Comparing this feature with observed rotation curves constrains the collisionality of our model's DM particle, and Bullet Cluster measurements constrain the scattering cross section. Both ultimately can be cast as constraints on the particle's mass. We find these two constraints cannot be satisfied simultaneously in any realistic halo model - and hence dark matter cannot be a repulsive boson in thermal equilibrium.

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Ed ~ The total amount of bosonic matter can be calculated by measuring the photon density. And all the bosonic matter has been accounted for, thus we already know that dark matter is not a form of bosonic matter...

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Dwarf galaxies suggest dark matter theory may be wrong

Scientists' predictions about the mysterious dark matter purported to make up most of the mass of the Universe may have to be revised.
Research on dwarf galaxies suggests they cannot form in the way they do if dark matter exists in the form that the most common model requires it to.
That may mean that the Large Hadron Collider will not be able to spot it.
Leading cosmologist Carlos Frenk spoke of the "disturbing" developments at the British Science Festival in Bradford.
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