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Planck sees a cosmic journey 13 billion years in the making

Cosmologists using data from ESA's Planck satellite have compiled the first all-sky image of the distribution of dark matter across the entire history of the Universe as seen projected on the sky. This is made possible by analysing the tiny distortions imprinted on the photons of the Cosmic Microwave Background (CMB) by the gravitational lensing effect of massive cosmic structures. As photons travelled through these structures, which consist primarily of dark matter, their paths became bent, slightly changing the pattern of the CMB. Although noisy, this image is the first measurement performed over almost the whole sky of the gravitational potential that distorts the CMB, and is one of the highlights of Planck's cosmological results. With these unique data, cosmologists can investigate 13 billion years of the formation of structure in the Universe. The data agree very well with the expectations from the leading cosmological model that describes the origin and evolution of cosmic structure in the Universe
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Title: A Dark-Disk Universe
Authors: JiJi Fan, Andrey Katz, Lisa Randall, Matthew Reece

We point out that current constraints on dark matter imply only that the majority of dark matter is cold and collisionless. A subdominant fraction of dark matter could have much stronger interactions. In particular, it could interact in a manner that dissipates energy, thereby cooling into a rotationally-supported disk, much as baryons do. We call this proposed new dark matter component Double-Disk Dark Matter (DDDM). We argue that DDDM could constitute a fraction of all matter roughly as large as the fraction in baryons, and that it could be detected through its gravitational effects on the motion of stars in galaxies, for example. Furthermore, if DDDM can annihilate to gamma rays, it would give rise to an indirect detection signal distributed across the sky that differs dramatically from that predicted for ordinary dark matter. DDDM and more general partially interacting dark matter scenarios provide a large unexplored space of testable new physics ideas.

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Title: A new probe of dark matter properties: gravitational waves from an intermediate mass black hole embedded in a dark matter mini-spike
Authors: Kazunari Eda, Yousuke Itoh, Sachiko Kuroyanagi, Joseph Silk

An intermediate mass black hole (IMBH) may have a dark matter (DM) mini-halo around it and develop a spiky structure within less than a parsec from the IMBH. When a stellar mass object is captured by the mini-halo, it eventually infalls into such an IMBH due to gravitational wave back reaction which in turn could be observed directly by future space-borne gravitational wave experiments such as eLISA/NGO. In this paper, we show that the GW detectability strongly depends on the radial profile of the DM distribution. So if the GW is detected, the power index, that is, the DM density distribution would be determined very accurately. The DM density distribution obtained would make it clear how the IMBH has evolved from a seed BH and whether the IMBH has experienced major mergers in the past. Unlike the gamma ray observations of DM annihilation, GW is just sensitive to the radial profile of the DM distribution and even to non-interacting DM. Hence the effect we demonstrate here can be used as a new and powerful probe into DM properties.

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Dwarf planet Eris may reveal quantum gravity

The dwarf planet Eris, named for the Greek goddess of strife, could also bring down the most popular explanations for dark matter and dark energy. A well-established notion in physics his says that empty space is really a frothy, turbulent sea full of virtual particles - matter and antimatter that spring in and out of existence so fast that we can't see them. Dragan Hajdukovic, a physicist at CERN near Geneva, Switzerland, thinks these bubbling particles may have opposing gravitational charges, similar to electrical charges. In the presence of a gravitational field, the particles would generate a secondary field, which, in the case of galaxies, could explain the mass discrepancy.
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Revolutionary theory of dark matter

The universe abounds with dark matter. Nobody knows what it consists of. UiO physicists have now launched a very hard mathematical explanation that could solve the mystery once and for all.
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Title: From gamma ray line signals of dark matter to the LHC 
Authors: Joachim Kopp, Ethan T. Neil, Reinard Primulando, Jure Zupan 

We explore the relationship between astrophysical gamma-ray signals and LHC signatures for a class of phenomenologically successful secluded dark matter models, motivated by recent evidence for a ~130 GeV gamma-ray line. We consider in detail scenarios in which interactions between the dark sector and the standard model are mediated by a vev-less scalar field \phi, transforming as an N-plet (N > 3) under SU(2)_L. Since some of the component fields of \phi carry large electric charges, loop induced dark matter annihilation to \gamma \gamma and \gamma Z can be enhanced without the need for non-perturbatively large couplings, and without overproduction of continuum gamma-rays from other final states. We discuss prospects for other experimental tests, including dark matter-nucleon scattering and production of \phi at the LHC, where future searches for anomalous charged tracks may be sensitive. The first LHC hints could come from the Higgs sector, where loop corrections involving \phi lead to significantly modified h to \gamma \gamma and h to \gamma Z branching ratios.

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Hints of new dark force seen in galactic smash-ups

Colliding clusters of galaxies may hold clues to a mysterious dark force at work in the universe. This force would act only on invisible dark matter, the enigmatic stuff that makes up 86 per cent of the mass in the universe.
Dark matter famously refuses to interact with ordinary matter except via gravity, so theorists had assumed that its particles would be just as aloof with each other. But new observations suggest that dark matter interacts significantly with itself, while leaving regular matter out of the conversation.

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Title: A new mechanism for dark matter generation from an interacting cosmological constant
Authors: Murli Manohar Verma

We propose an alternative scenario for the dark matter generation from an evolving cosmological constant which interacts with the dominant background in certain intermediate phase of the universe, and relaxes to the observed small value at present. In this way, it is shown that the interaction of the cosmological constant with the radiation or matter might generate the dark matter densities with a varied mass spectrum in the universe with their characteristic arc-like frozen signatures on the Cosmic Microwave Background Radiation (CMBR). This approach also suggests a possible solution to the long standing cosmological constant problem.

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Title: First asteroseismic limits on the nature of dark matter
Authors: Jordi Casanellas, Ilídio Lopes

We report the first constraints on the properties of weakly interacting low-mass dark matter (DM) particles using asteroseismology. The additional energy transport mechanism due to accumulated asymmetric DM particles modifies the central temperature and density of low-mass stars and suppresses the convective core expected in 1.1-1.3 Ms stars even for an environmental DM density as low as the expected in the solar neighbourhood. An asteroseismic modelling of the stars KIC 8006161, HD 52265 and Alpha Cen B revealed small frequency separations significantly deviated from the observations, leading to the exclusion of a region of the DM parameter space mass vs. spin-dependent DM-proton scattering cross section comparable with present experimental constraints.

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Title: Disk Stability and Neutral Hydrogen as a Tracer of Dark Matter
Authors: Gerhardt R. Meurer (1), Zheng Zheng (2), W.J.G. de Blok (3,4) ((1) ICRAR, The University of Western Australia, (2) The Johns Hopkins University, (3) ASTRON, (4) ACGC, University of Cape Town)

We derive the projected surface mass distribution Sigma_M for spherically symmetric mass distributions having an arbitrary rotation curve. For a galaxy with a flat rotation curve and an ISM disk having a constant Toomre stability parameter, Q, the ISM surface mass density Sigma_g as well as Sigma_M both fall off as 1/R. We use published data on a sample of 20 well studied galaxies to show that ISM disks do maintain a constant Q over radii usually encompassing more than 50% of the HI mass. The power law slope in Sigma_g covers a range of exponents and is well correlated with the slope in the epicyclic frequency. This implies that the ISM disk is responding to the potential, and hence that secular evolution is important for setting the structure of ISM disks. We show that the gas to total mass ratio should be anti-correlated with the maximum rotational velocity, and that the sample falls on the expected relationship. A very steep fall off in Sigma_g is required at the outermost radii to keep the mass and angular momentum content finite for typical rotation curve shapes, and is observed. The observation that HI traces dark matter over a significant range of radii in galaxies is thus due to the disks stabilising themselves in a normal dark matter dominated potential. This explanation is consistent with the cold dark matter paradigm.

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