Gert Hütsi

PPPC 4 DM ID: A Poor Particle Physicist Cookbook for Dark Matter Indirect Detection

We correct a few mistakes of the original version of this work (notably related to the computations of extragalactic gamma rays), while at the same time improving and upgrading other aspects (notably as a consequence of the discovery of the higgs boson at the LHC). A brief list of the main changes is: - We include a higgs boson channel hh with mass mh = 125 GeV. All previous channels hmhm are removed. - We correct the formulae for the computation of extragalactic gamma rays (fixing in particular the redshift dependence) as well as the numerical computations (also including a corrected impact of absorption). - We provide a new version of the Optical Depth function, employing updated models of Extragalactic Background Light (EBL) and fixing the redshift dependence. All these corrections and updates are reflected on the numerical ingredients provided on the website; they correspond to Release 2.0.

Constraints on leptonically annihilating dark matter from reionization and extragalactic gamma background

The PAMELA, Fermi and HESS experiments (PFH) have shown anomalous excesses in the cosmic positron and electron fluxes. A very exciting possibility is that those excesses are due to annihilating dark matter (DM). In this paper we calculate constraints on leptonically annihilating DM using observational data on diffuse extragalactic gamma-ray background and measurements of the optical depth to the last-scattering surface, and compare those with the PFH favored region in the m_{DM} - plane. Having specified the detailed form of the energy input with PYTHIA Monte Carlo tools we solve the radiative transfer equation which allows us to determine the amount of energy being absorbed by the cosmic medium and also the amount left over for the diffuse gamma background. We find that the constraints from the optical depth measurements are able to rule out the PFH favored region fully for the \tau^{-}+\tau^{+} annihilation channel and almost fully for the \mu^{-}+\mu^{+} annihilation channel. It turns out that those constraints are quite robust with almost no dependence on low redshift clustering boost. The constraints from the gamma-ray background are sensitive to the assumed halo concentration model and, for the power law model, rule out the PFH favored region for all leptonic annihilation channels. We also find that it is possible to have models that fully ionize the Universe at low redshifts. However, those models produce too large free electron fractions at z > ~100 and are in conflict with the optical depth measurements. Also, the magnitude of the annihilation cross-section in those cases is larger than suggested by the PFH data.

Dynamically Induced Planck Scale and Inflation

A bstractTheories where the Planck scale is dynamically generated from dimensionless interactions provide predictive inflationary potentials and super-Planckian field variations. We first study the minimal single field realisation in the low-energy effective field theory limit, finding the predictions ns ≈ 0.96 for the spectral index and r ≈ 0.13 for the tensor-to-scalar ratio, which can be reduced down to ≈ 0.04 in presence of large couplings. Next we consider agravity as a dimensionless quantum gravity theory finding a multifield inflation that converges towards an attractor trajectory and predicts ns ≈ 0.96 and 0.003 < r < 0.13, interpolating between the quadratic and Starobinsky inflation. These theories relate the smallness of the weak scale to the smallness of inflationary perturbations: both arise naturally because of small couplings, implying a reheating temperature of 107−9 GeV. A measurement of r by Keck/Bicep3 would give us information on quantum gravity in the dimensionless scenario.

Clusters and superclusters in the Sloan Digital Sky Survey

We apply the 2-dimensional high-resolution density field of galaxies of the Early Data Release of the Sloan Digital Sky Survey with a smoothing lengths 0.8 h −1 Mpc to extract clusters and groups of galaxies, and a low-resolution field with smoothing lengths 10 h −1 Mpc to extract superclusters of galaxies. We investigate properties of density field clusters and su- perclusters and compare properties of these clusters and superclusters with Abell clusters, and superclusters found on the basis of Abell clusters. We found that clusters in high-density environment have a luminosity a factor of 5−10 higher than in low- density environment. There exists a large anisotropy between the SDSS Northern and Southern sample in the properties of clusters and superclusters: most luminous clusters and superclusters in the Northern sample are a factor of 2 more luminous than the respective systems in the Southern sample.

Implications of the Fermi-LAT diffuse gamma-ray measurements on annihilating or decaying dark matter

We analyze the recently published Fermi-LAT diffuse gamma-ray measurements in the context of leptonically annihilating or decaying dark matter (DM) with the aim to explain simultaneously the isotropic diffuse gamma-ray and the PAMELA, Fermi and HESS (PFH) anomalous e± data. Five different DM annihilation/decay channels 2e, 2μ, 2τ, 4e, or 4μ (the latter two via an intermediate light particle ) are generated with PYTHIA. We calculate both the Galactic and extragalactic prompt and inverse Compton (IC) contributions to the resulting gamma-ray spectra. To find the Galactic IC spectra we use the interstellar radiation field model from the latest release of GALPROP. For the extragalactic signal we show that the amplitude of the prompt gamma-emission is very sensitive to the assumed model for the extragalactic background light. For our Galaxy we use the Einasto, NFW and cored isothermal DM density profiles and include the effects of DM substructure assuming a simple subhalo model. Our calculations show that for the annihilating DM the extragalactic gamma-ray signal can dominate only if rather extreme power-law concentration-mass relation C(M) is used, while more realistic C(M) relations make the extragalactic component comparable or subdominant to the Galactic signal. For the decaying DM the Galactic signal always exceeds the extragalactic one. In the case of annihilating DM the PFH favored parameters can be ruled out by gamma-ray constraints only if power-law C(M) relation is assumed. For DM decaying into 2μ or 4μ the PFH favored DM parameters are not in conflict with the gamma-ray data. We find that, due to the (almost) featureless Galactic IC spectrum and the DM halo substructure, annihilating DM may give a good simultaneous fit to the isotropic diffuse gamma-ray and to the PFH e± data without being in clear conflict with the other Fermi-LAT gamma-ray measurements.

Superclusters of galaxies from the 2dF redshift survey. II. Comparison with simulations

We investigate properties of superclusters of galaxies found on the basis of the 2dF Galaxy Redshift Survey, and compare them with properties of superclusters from the Millennium Simulation.We study the dependence of various characteristics of superclusters on their distance from the observer, on their total luminosity, and on their multiplicity. The multiplicity is defined by the number of Density Field (DF) clusters in superclusters. Using the multiplicity we divide superclusters into four richness classes: poor, medium, rich and extremely rich.We show that superclusters are asymmetrical and have multi-branching filamentary structure, with the degree of asymmetry and filamentarity being higher for the more luminous and richer superclusters. The comparison of real superclusters with Millennium superclusters shows that most properties of simulated superclusters agree very well with real data, the main differences being in the luminosity and multiplicity distributions.

Luminous superclusters: remnants from inflation?

Aims. We compile a supercluster sample using the Sloan Digital Sky Survey Data Release 4, and reanalyse supercluster samples found for the 2dF Galaxy Redshift Survey and for simulated galaxies of the Millennium Run. Methods. We find for all supercluster samples Density Field (DF) clusters, which represent high-density peaks of the class of Abell clusters, and use median luminosities of richness class 1 DF-clusters to calculate relative luminosity functions. Results. We show that the fraction of very luminous superclusters in real samples is about five times greater than in simulated samples. Conclusions. Superclusters are generated by large-scale density perturbations that evolve very slowly. The absence of very luminous superclusters in simulations can be explained either by incorrect treatment of large-scale perturbations, or by some yet unknown processes in the very early Universe.

Constraint on the cosmological f (R) model from the multipole power spectrum of the SDSS luminous red galaxy sample and prospects for a future redshift survey

A constraint on the viable

Superclusters of galaxies in the 2dF redshift survey - III. The properties of galaxies in superclusters

f(R)

Towards understanding the structure of voids in the cosmic web

model is investigated by confronting theoretical predictions with the multipole power spectrum of the luminous red galaxy sample of the Sloan Digital Sky Survey, data release 7. We obtain a constraint on the Compton wavelength parameter of the