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Minimal atomic dark matter with its distinctive cooling mechanisms offers an instructive framework for understanding the potential impact of dark matter on small-scale structure formation and early cosmology. The model consists of two…
We propose a comprehensive theory of dark matter that explains the recent proliferation of unexpected observations in high-energy astrophysics. Cosmic ray spectra from ATIC and PAMELA require a WIMP with mass M_chi ~ 500 - 800 GeV that…
If the gamma-ray excess from the galactic center reported by Fermi-LAT is a signal from annihilating dark matter, one must question why a similar excess has not been observed in dwarf spheroidal galaxies. We use this observation to place…
Moduli fields, a natural prediction of any supergravity and superstring-inspired supersymmetry theory, may lead to a prolonged period of matter domination in the early Universe. This can be observationally viable provided the moduli decay…
Although the spectrum of primordial fluctuations has been accurately measured on scales above $\sim 0.1~\rm{Mpc}$, only upper limits exist on smaller scales. In this study, we investigate generic monochromatic enhancements to the…
We study the annihilating dark matter contribution to the extra-galactic diffuse gamma-ray background spectrum, motivated by the recent observations of cosmic-ray positron/electron anomalies. The observed diffuse gamma-ray flux provides…
Some theoretical models for the early Universe predict a spike-type enhancement in the primordial power spectrum on a small scale, which would result in forming early-formed dark matter halos~(EFHs). Some recent studies have claimed to have…
The nature of the Isotropic $\gamma$-ray Background (IGRB) measured by the Large Area Telescope (LAT) on the Fermi $\gamma$-ray space Telescope ({\it Fermi}) remains partially unexplained. Non-negligible contributions may originate from…
In the cold dark matter scenario, galactic dark matter halos are populated with a large number of smaller subhalos. Previous work has shown that dark matter annihilations in subhalos can generate a distinctive, non-Poisson signal in the…
We propose a novel and simple scenario to explain baryon asymmetry and dark matter (DM) by utilizing an early matter-dominated era (EMDE) caused by a heavy metastable particle. Within the EMDE, lack of pressure enhances the formation of…
We search for excess gamma-ray emission coincident with the positions of confirmed and candidate Milky Way satellite galaxies using 6 years of data from the Fermi Large Area Telescope (LAT). Our sample of 45 stellar systems includes 28…
Excesses on positron and electron fluxes measured by ATIC, and the PAMELA and Fermi--LAT telescopes can be explained by dark matter annihilation in our Galaxy. However, this requires large boosts on the dark matter annihilation rate. There…
The fast developments of radio astronomy open a new window to explore the properties of Dark Matter (DM). The recent direct imaging of the supermassive black hole (SMBH) at the center of M87 radio galaxy by the Event Horizon Telescope (EHT)…
The existence of an early matter-dominated epoch prior to the Big Bang Nucleosynthesis may lead to a scenario where the thermal dark matter cools faster than plasma before the radiation-dominated era begins. In the radiation-dominated…
The extragalactic dark matter (DM) annihilation signal depends on the product of the clumping factor, <\delta^2>, and the velocity-weighted annihilation cross section, \sigma v. This "clumping factor-\sigma v" degeneracy can be broken by…
New bounds on decaying Dark Matter are derived from the gamma-ray measurements of (i) the isotropic residual (extragalactic) background by Fermi and (ii) the Fornax galaxy cluster by H.E.S.S. We find that those from (i) are among the most…
Observations by ARCADE-2 and other telescopes sensitive to low frequency radiation have revealed the presence of an isotropic radio background with a hard spectral index. The intensity of this observed background is found to exceed the flux…
The possibility to use $\gamma$--ray data from the Galactic Center (GC) to constrain the cosmological evolution of the Universe in a phase prior to primordial nucleosyntesis, namely around the time of cold dark matter (CDM) decoupling, is…
The annihilation of dark matter (DM) in the Galaxy could produce specific imprints on the spectra of antimatter species in Galactic cosmic rays, which could be detected by upcoming experiments such as PAMELA and AMS02. Recent studies show…
Observation of gamma-rays from dwarf galaxies is an effective way to search for particle dark matter. Using 4-year data of Fermi-LAT observations on a series of Milky Way satellites, we develop a general way to search for the signals from…