Regardless of the precise nature of dark matter (DM), its distribution in the central regions of galaxies remains poorly constrained at present. In particular, DM halos may be significantly affected by the presence of central supermassive black holes, leading to the possible formation of high density spikes. Two objects are of particular interest in this context: Sgr A* at the center of the...
Longstanding anomalies in astrophysical observations on small scales suggest that dark matter might not be collisionless, as is commonly assumed, but could have sizable self-interactions. For the first time, we probe the hypothesis of self-interacting dark matter (SIDM) at intermediate scales between galaxies and galaxy clusters. To model the SIDM halo density profiles, we employ an...
Self-interacting Dark Matter (SIDM) could have a number of striking observable effects, including modifications to the dark matter density on galactic and sub-galactic scales. Recent studies have revealed both ultra-compact and ultra-diffuse satellite dwarf galaxies within the Milky Way; this degree of diversity seems challenging to explain if the dark matter is collisionless and cold. I will...
The observed Lyman-α flux power spectrum (FPS) is suppressed on scales below ∼ 30 km s−1. This cutoff could be due to the high temperature, T0, and pressure, p0, of
the absorbing gas or, alternatively, it could reflect the free streaming of dark matter particles in the early universe. We perform a set of very high resolution cosmological hydrodynamic simulations in which we vary T0, p0 and...
Despite its remarkable success, the standard LCDM paradigm has been challenged lately by potential tensions in the Hubble Constant measurements, as well as a slight mismatch between simulations and observations on smaller scales. This has reinvigorated interest in beyond-LCDM models, such as Dark Matter interacting with an additional dark sector. These interactions result in a suppression of...
The number of extra relativistic degrees of freedom, $\Delta N_{\rm eff}$ , has recently received attention as a possible way to alleviate the Hubble tension. Non-standard values, i.e. $\Delta N_{\rm eff} \neq 0$, can arise from different physical origins, such as the presence of additional ultra-relativistic species or non-standard values of the temperature ratio between photons and...
Primordial black holes (PBH) comprising some fraction of the Universe's dark matter is a potentially interesting alternative to the more standard particle based dark matter. If the fraction is large, PBHs can significantly alter how and when nonlinear structures develop. If it is small, they could provide potentially interesting constraints on WIMPs and/or seed the super massive black holes...
It has been shown that the longitudinal mode of a massive vector boson can be p\
roduced by inflationary fluctuations and account for the dark matter content of\
the Universe. In this work we examine the possibility of instead producing the\
transverse mode via the coupling ϕFF̃ between the inflaton and the vector field\
strength. Such a coupling leads to a tachyonic instability and...
I will discuss the preferred initial conditions that scalar field fluctuations during cosmic inflation generically place for post-inflationary, non-thermal dark matter (DM) production. I will show that accumulation of quantum fluctuations during inflation can account for all or part of DM. I will also discuss the DM isocurvature perturbations that are unavoidably generated in such scenarios...
In my talk I will discuss the dependence of the dark matter production mechanism in the early universe on its coupling to the Standard Model and mediator. For illustration, I will focus on the case of compressed mass spectrum dark matter scenario and show that we can continuously go from freeze-in to freeze-out with an intermediate stage of conversion driven freeze-out. In the latter case,...
Many well-motivated extensions of the standard model contain a gauge singlet scalar field which mixes with the Higgs boson. The new scalar naturally mediates the interactions between dark and visible matter. I will focus one the GeV mass window, which features exciting signatures of dark matter and the light mediator at upcoming direct detection and accelerator experiments. This mass range...
An excess of cosmic positrons above 10 GeV with respect to the spallation reaction of cosmic rays with the interstellar medium has been measured by AMS-02 with unprecedented precision. Recently, a gamma-ray halo in the direction of Geminga and Monogem pulsars has been detected by HAWC. These observations can be interpreted with positrons and electrons accelerated by pulsar wind nebulae (PWNe),...
Light antinuclei may be generated in dark matter annihilations or decays, offering a potential method of identifying the nature of dark matter. However, current estimations of the antinucleus fluxes has large uncertainties due to, amongst other, the antinucleon formation models. Today it is common to use the coalescence model on an event-by-event basis in a Monte Carlo framework when...
In recent years, several investigations have pointed towards an excess in the cosmic-ray antiproton data reported by the AMS-02 Collaboration. The interpretation of this result, which could potentially represent a dark matter signal, requires a thorough understanding of the systematic uncertainties associated with it. In this talk I will focus on one of these uncertainties, the one arising...
Global fits of primary and secondary cosmic-ray (CR) fluxes measured by the AMS-02 experiment provide a powerful tool to probe the existence of exotic sources of antimatter in our Galaxy, such as annihilation or decay of dark matter (DM). Previous analyses derived strong constraints on the annihilation cross section of a potential DM particle with masses above a couple of hundred GeV, while...
Dark matter in cosmic structures is expected to produce signals
originated from its particle physics nature, among which the electromagnetic
emission represents a relevant opportunity, whose intensity is directly linked
to the amount of dark matter in galaxies and clusters. On the other hand, this
emission is very faint, thus contributing only at the unresolved level. These...
The dissection of the gamma-ray sky into point sources and diffuse components is a valuable tool to search for new physics, such as dark matter signals. In the recent past, it has been shown that statistical analysis methods can excel the sensitivity of classic source detection approaches. In this contribution we discuss the application of photon count statistics to dark matter searches in...
I will review the status of cosmological searches for dark matter-baryon interactions, summarizing the best current limits on scattering of sub-GeV particle candidates with protons derived from the CMB anisotropy measurements. I will then present stringent new bounds on the same physics, inferred recently from the observed population of the Milky Way satellite galaxies. I will highlight...
We present MadDM v.3.0, a numerical tool to compute particle dark matter observables. The new version features a comprehensive and automated framework for dark matter searches at the interface of collider physics, astrophysics and cosmology and is deployed as a plugin of the MadGraph5_aMC@NLO platform, inheriting most of its features. With respect to the previous version, MadDM v.3.0 now...
Paleo-detectors are a proposed experimental technique where one would search for the traces of nuclear recoils in ancient minerals. Modern read out technologies should allow to reach ~ 1 keV nuclear recoil energy thresholds for exposures as large as 100 g Gyr = 100 kt yr. Recently, we investigated the sensitivity of paleo detectors for dark matter. In this talk, I will demonstrate that...
A large experimental program is underway to extend the sensitivity of direct detection experiments, searching for interaction of Dark Matter with nuclei, down to the neutrino floor. However, such experiments are becoming increasingly difficult and costly due to the large target masses and exquisite background rejection needed for the necessary improvements in sensitivity. We investigate an...
The axion is a pseudo-Goldstone boson of a new spontaneously broken symmetry, the Peccei-Quinn symmetry. If the symmetry is broken after inflation, topological strings are formed. As they slowly decay, they emit axion radiation. The axion production analysis is complicated because topological defect structures, global strings, appear in the axionic field and because the only reliable way to...
In this talk, I will discuss the mechanisms and effects of capture of self-annihilating Superheavy Dark Matter by the first stars (PopIII stars), extending previous analysis on the case of WIMP Dark Matter. Pop III stars form as a consequence of hydrogen cloud collapse at the center of DM halos at redshifts of z~10-20. They are typically massive, sometimes exceeding 1000 solar masses, and...
High energy neutrinos are produced in very distant sources of the Universe, such as Gamma Ray Bursts and Active Galactic Nuclei (AGN). Considering the neutrino magnetic moment, and the strong magnetic fields inside these objects, we study a possible conversion from active neutrinos to sterile neutrinos. We also include the cosmological effects like the expansion of the Universe, where the...
I will discuss the cosmology and LHC phenomenology of a consistent, strongly interacting dark sector coupled to Standard Model particles through a Z' mediator. I will lay out the requirements for the model to be cosmologically viable, consider the dominant freeze-out processes, and discuss bounds from direct detection. Using this consistent SIMP sector, I will then focus on the sensitivity of...
Incorporating three generations of right-handed Majorana neutrinos to quintessential inflation, we construct a model which simultaneously explains inflation, dark energy, dark matter and baryogenesis. These right-handed neutrinos have hierarchical masses $M_3 \sim 10^{13}$GeV, $M_2 \sim 10^{11}$GeV, $M_1 \sim 10$keV and are produced by gravitational particle production in the kination regime...
In this presentation, I will show the importance of the longitudinal polarization of the dark photon, or equivalently, the Goldstone in the formation of the dark matter bound state. The bound state formation through the "mono-pole" emission of a longitudinal dark photon will dominate the re-annihilation process, unlike the usual dark matter formation process calculations. I will also show some...
The DARWIN experiment is a proposed next-generation multi-purpose dark matter observatory. This dual-phase Time Projection Chamber will comprise a 50 tonne liquid xenon target, allowing to probe the experimentally accessible parameter space for Weakly Interacting Massive Particles (WIMPs) in a wide mass range until neutrino interactions with the target become an irreducible background. With a...
Dwarf spheroidal galaxies are excellent targets in gamma-ray searches for dark matter. We consider dark matter searches in dwarf spheroidal galaxies (dSphs) with the Cherenkov Telescope Array (CTA). The aim of this work is to reveal a quantitative and precise dependence of the accessible dark matter annihilation cross-sections on the dark matter density profiles of dSphs and on the distance to...
Several modern theories hypothesize that dark matter condenses to a superfluid phase around galaxies. If true, one key distinction from particle dark matter is dynamical friction, a process by which a massive perturber moving through a cloud of matter is slowed by the gravitational attraction to its own wake. I will describe the steady-state dynamical friction of a perturber moving through a...
Strong lenses are systems in which the light from a background source is deflected by a foreground galaxy or group of galaxies, resulting in multiple images of the background source. These images are also usually heavily distorted, acquiring the shape of rings or arcs. Study of these images provides us unique information about the distribution of matter (baryonic plus dark) within the...
Determining the nature of dark matter remains an unsolved puzzle of modern day physics. In recent years, the possibility that dark matter consists of several different components has received increased attention.
If one of these components consists of particles at the keV-scale, it can have non-negligible impact on cosmological observables.
In this talk, I will present how a decaying keV scale...
We study in detail simple extension of the freeze-in mechanism based on kinematically forbidden production of dark matter through plasma effects. Focusing on Higgs portal model, where the dark matter is produced via forbidden decays of a scalar coupled to the Higgs, current and future collider, cosmological, and astrophysical probes are considered.
Transition amplitudes describing dark-matter annihilation processes through a resonance may become highly inaccurate close to a production threshold if a Breit-Wigner propagator with a constant width is used. To partially overcome this problem, the BW propagator needs to be modified by including a momentum dependent decay width. However, such an approach to resonant transition amplitudes...
We study the monopole dark matter (MDM) emerging from a spontaneous breakdown of non- abelian gauge symmetry in the hidden sector. We assume that this hidden MDM was produced as a topological defect during a second-order phase transition in the early universe, and its stability is guaranteed by the topological nature. In particular, we introduce an axion-like particle (ALP), which mediates the...
The dark matter (DM) direct detection experiments give a strong upper bound on the DM-nucleon scattering cross section. In fermionic DM models with pseudoscalar mediators, the tree-level amplitude for the DM-nucleon elastic scattering is suppressed by the momentum transfer in the non-relativistic limit. This is a nice feature to avoid the constraint from the direct detection experiments....
Solar dark matter (DM) searches offer a complementary way of studying the nature of DM particles and their potential interactions with ordinary matter. However, the resulting neutrinos fluxes are significantly attenuated at high energies due to their charged current interactions with the solar material. In this talk, I will present results (in a model-independent manner) from a scenario where...
The global contribution of unresolved gamma-ray point sources to the extragalactic gamma-ray background has recently been measured through analyses employing the statistical properties of the observed gamma-ray counts and their anisotropies down to lower gamma-ray fluxes with respect to standard source detection techniques. However, the contribution from each specific source classes to the...
We discuss the dynamics and phenomenology of an oscillating scalar field coupled to the Higgs boson that accounts for the dark matter in the Universe. The model assumes an underlying scale invariance such that the scalar field only acquires mass after the electroweak phase transition, behaving as dark radiation before the latter takes place. While for a positive coupling to the Higgs field the...
We discuss a setup in which freeze-in dark matter production can be probed through dark matter decay.
If dark matter consists of two or more flavors, transitions between dark matter particles can serve as a probe of the coupling that sets the relic abundance and give rise to gamma-ray spectral features.
In light of increasing constraints on WIMP models, exciting alternatives have begun to gain traction. One example is freeze-in models which rely on extremely small dark-visible couplings to produce dark matter from the visible sector. Such non-standard dark matter models can be probed (despite the tiny couplings) by direct detection experiments if they include a light mediator. Moreover,...
