The Cosmic Neutrino Background is a prediction of the standard cosmological model, but it has been never observed directly. Experiments with the aim of detecting relic CNB neutrinos are under development. For such experiments, the expected event rate depends on the local number density of relic neutrinos. Since massive neutrinos can be attracted by the gravitational potential of our galaxy and...
Pseudo-Dirac neutrinos are pairs of maximally-mixed Majorana neutrinos with tiny mass difference between the active and the sterile states in each pair. Their oscillation phenomenology is different from that of active neutrinos. Assuming blazars to be the source of astrophysical neutrinos, we construct all-sky maps of neutrino flavor compositions resulting from oscillations of pseudo-Dirac...
Compact stellar objects such as neutron stars (NS) are ideal places for capturing dark matter (DM) particles. We study the effect of self-interacting DM captured by the nearby NS that can reheat it to an appreciated surface temperature through absorbing the energy released due to DM annihilation. When DM-nucleon cross section $\sigma_{\chi n}$ is small enough, DM self-interaction will take...
We study SN1987A constraints on the interactions between Standard Model fermions and dark vector boson. We consider a more general scenario that the dark boson mixes with Standard Model (SM) gauge bosons through both kinetic and mass mixing terms in the Lagrangian. Hence dark boson couples to SM fermions via vector and axial-vector couplings. Such couplings induce reactions $N+N\to N+N+Z_d$...
We study a class of models in which the Standard Model (SM) is augmented by vector-like leptons: one doublet and a singlet, which are odd under an unbroken discrete Z_2 symmetry. As a result, the neutral component of these additional vector-like leptons are stable and behave as dark matter. We study the phenomenological constraints on the model parameters and elucidate the parameter space...
In this this talk, I will discus a leptophilic dark matter scenario involving feeble dark matter coupling to the Standard Model (SM) and compressed dark matter-mediator mass spectrum. I will consider a simplified model where the SM is extended with one Majorana fermion, the dark matter, and one charged scalar, the mediator, coupling to the SM leptons through a Yukawa interaction. I will first...
Deformed relativistic kinematics, expected to emerge in a flat-spacetime limit of quantum gravity, predicts the Planck-scale violation of discrete symmeries, in particular the CPT symmetry.
Momentum-dependent deformations of the action of CPT are derived from the kappa-deformed Poincare algebra.
In this approach, deformation of CPT symmetry leads to a subtle violation of
Lorentz symmetry.
This...
Precision results on cosmic-ray electrons are presented in the energy range from 0.5 GeV to 1.4 TeV based on 28.1 million electrons collected by the Alpha Magnetic Spectrometer on the International Space Station. In the entire energy range the electron and positron spectra have distinctly different magnitudes and energy dependences. The electron flux exhibits a significant excess starting from...
In this talk, I will discuss consequences of the potential detection of anti-helium-3 and -4 events by AMS-02. After showing that spallation from primary hydrogen and helium nuclei onto the ISM cannot account for the measured fluxes, I will argue that dark matter annihilation or decay face similar difficulties in explaining these events. I will then entertain the possibility that these events...
Global fits of primary and secondary cosmic-ray (CR) fluxes measured by AMS-02
have great potential to study CR propagation models and search for exotic
sources of antimatter such as annihilating dark matter (DM). Previous studies
of AMS-02 antiprotons revealed a possible hint for a DM signal which, however,
could be affected by systematic uncertainties. To test the robustness of such a
DM...
The Dark Energy Survey (DES) is a large galaxy survey designed to address the fundamental question of the accelerating expansion of the universe and uncover the nature of the dark energy. It has mapped 1/8 of the sky in the southern hemisphere to an unprecedented depth for such a wide area. The talk will present the most recent measurements of the cosmological parameters from this project,...
Identifying the nature of the late-time accelerated expansion of our Universe remains a difficult puzzle to cosmology. Scalar-tensor modifications of gravity have long been considered as an alternative explanation to the cosmological constant. I will first discuss how the direct detection of gravitational waves and the measurement of electromagnetic counterparts, confirming a luminal speed of...
Euclid is the M2 mission of ESA's Cosmic Vision program dedicated to the study of the dark universe: Dark Matter and Dark Energy, with launch scheduled for 2022. Euclid will observe 15,000 square degrees of extragalactic sky in the visible band with resolution of 0.1arcsec (VIS), in IR photometry for the Y, J, H bands and in slitless spectroscopy between 1 and 2 microns (NISP). Euclid will be...
Structure formation at small cosmological scales provides an important frontier for Dark Matter (DM) research.
So far, many non-cold DM (nCDM) candidates have been proposed in order to give a better description of the structure formation and distribution at small scales, with respect to the standard cold DM (CDM) model.
The details of the small-scale power suppression depend on the DM...
We consider in this work a Slotheon scalar field for Dark Energy. A Slotheon
field is inspired by extra dimensional models of Dvali, Gabadadze and
Porrati (DGP) related to brane world. In the decoupling limit
of this model, the DGP theory in Minkowski space-time is described by a
scalar field that obeys a shift symmetry. When extended to curved space time
this scalar field is termed as...
To the zeroth order in gravitational interactions, the averaged QCD (quark-gluon) vacuum condensate density is dynamically self-screened and is eliminated at macroscopic space-time separations. We argue that the observable cosmological constant can then be generated as a quantum gravity correction to QCD vacuum energy density after the QCD phase transition epoch. In order to incorporate the...
-
We can perform the geometric argument of general relativity principle on (unstable) Riemann space-time just inspired by nonlinear representation of supersymmetry(NLSUSY), whose tangent space is specified by Grassmann degrees of freedom ψ of SL(2,C) besides the ordinary Minkowski one xa of SO(1,3) and obtain straightforwardly new Einstein-Hilbert(EH)-type action with global NLSUSY...
