Found 1304 results, showing the newest relevant preprints. Sort by relevancy only.Update me on new preprints

Density perturbation in interacting holographic **dark** energy model

The present work deals with the evolution of the density contrasts for a cosmological model where along with the standard cold

**dark****matter**(CDM), the present Universe also contains holographic dark energy (HDE). Expand abstract. The present work deals with the evolution of the density contrasts for a cosmological model where along with the standard cold

**dark****matter**(CDM), the present Universe also contains holographic**dark**energy (HDE). The characteristic infra-red (IR) cut-off is taken as the future event horizon. The HDE is allowed to interact with the CDM. The equations for the density contrasts are integrated numerically. It is found that irrespective of the presence of an interaction, the**matter**perturbation has growing modes. The HDE is also found to have growth of perturbation, so very much like the CDM, thus can also cluster. The interesting point to note is that the density contrast corresponding to HDE has a peak at recent past and is decaying at the present epoch. Another feature is that IR cut-off as the event horizon does not naturally produce accelerated expansion of the Universe in the presence of an interaction.7 days ago

4/10 relevant

arXiv

4/10 relevant

arXiv

Two-component asymmetric **dark** **matter** via bound states and freeze-in
decay

Assuming a particle-antiparticle asymmetry is initially shared by SM baryons and two

**dark****matter**components, we demonstrate that the existence of bound states among the heavy DM particles is able to transfer most of the asymmetry stored in the heavy component to the light one by late decay. Expand abstract. We propose a novel mechanism to realize two-component asymmetric

**dark****matter**of very different mass scales through bound state formation and late freeze-in decay. Assuming a particle-antiparticle asymmetry is initially shared by SM baryons and two**dark****matter**components, we demonstrate that the existence of bound states among the heavy DM particles is able to transfer most of the asymmetry stored in the heavy component to the light one by late decay. In this case, the energy densities of the two components can be comparable, and the correct relic density is reproduced.7 days ago

10/10 relevant

arXiv

10/10 relevant

arXiv

Signatures of **Dark** **Matter** in Cosmic-Ray Observations

For each case I will focus on various excesses reported in the literature which have been interpreted as possible hints of

**dark****matter**, and I will use them as examples to discuss theoretical aspects and analysis methodologies. Expand abstract. I provide a short review of the current status of indirect

**dark****matter**searches with gamma rays, charged cosmic rays and neutrinos. For each case I will focus on various excesses reported in the literature which have been interpreted as possible hints of**dark**matter, and I will use them as examples to discuss theoretical aspects and analysis methodologies.8 days ago

10/10 relevant

arXiv

10/10 relevant

arXiv

Primordial universe with the running cosmological constant

By using the handy model of Reduced Relativistic Gas for describing the

**Dark**Matter, we consider the dynamics of both cosmic background and linear perturbations and evaluate the impact of the vacuum decay on the**matter**power spectrum and to the first CMB peak. Expand abstract. Theoretically, the running of the cosmological constant in the IR region is not ruled out. On the other hand, from the QFT viewpoint, the energy released due to the variation of the cosmological constant in the late universe cannot go to the

**matter**sector. For this reason, the phenomenological bounds on such a running are not sufficiently restrictive. The situation can be different in the early universe when the gravitational field was sufficiently strong to provide an efficient creation of particles from the vacuum. We develop a framework for systematically exploring this possibility. It is supposed that the running occurs in the epoch when the**Dark****Matter**already decoupled and is expanding adiabatically, while baryons are approximately massless and can be abundantly created from vacuum due to the decay of vacuum energy. By using the handy model of Reduced Relativistic Gas for describing the**Dark**Matter, we consider the dynamics of both cosmic background and linear perturbations and evaluate the impact of the vacuum decay on the**matter**power spectrum and to the first CMB peak. Additionally, using the combined data of CMB+BAO+SNIa we find the best fit values for the free parameters of our model.8 days ago

4/10 relevant

arXiv

4/10 relevant

arXiv

Marked correlation functions in perturbation theory

We develop perturbation theory approaches to model the marked correlation function constructed to up-weight low density regions of the Universe, which might help distinguish modified gravity models from the standard cosmology model based on general relativity. Expand abstract.

We develop perturbation theory approaches to model the marked correlation function constructed to up-weight low density regions of the Universe, which might help distinguish modified gravity models from the standard cosmology model based on general relativity. Working within Convolution Lagrangian Perturbation Theory, we obtain that weighted correlation functions are expressible as double convolution integrals that we approximate using a combination of Eulerian and Lagrangian schemes. We find that different approaches agree within 1$\%$ on quasi non-linear scales. Compared with {\it N}-body simulations, the perturbation theory is found to provide accurate predictions for the marked correlation function of

**dark****matter**fields,**dark****matter**halos as well as Halo Occupation Distribution galaxies down to $30$ Mpc/h. These analytic approaches help to understand the degeneracy between the mark and the galaxy bias and find a way to maximize the differences among various cosmological models.8 days ago

4/10 relevant

arXiv

4/10 relevant

arXiv

Constraining the abundance of primordial black holes with gravitational lensing of gravitational waves at LIGO frequencies

Similarly, if a small percentage of the

**dark****matter**is in the form of microlenses with a few tens of solar masses, at sufficiently large magnification factors, all gravitational waves will show interference effects. Expand abstract. Gravitational waves from binary black holes that are gravitationally lensed can be distorted by small microlenses along the line of sight. Microlenses with masses of a few tens of solar masses, and that are close to a critical curve in the lens plane, can introduce a time delay of a few millisecond. Such time delay would result in distinctive interference patterns in the gravitational wave that can be measured with current experiments such as LIGO/Virgo. We consider the particular case of primordial black holes with masses between 5 and 50 solar masses acting as microlenses. We study the effect of a population of primordial black holes constituting a fraction of the

**dark**matter, and contained in a macrolens (galaxy or cluster), over gravitational waves that are being lensed by the combined effect of the macrolens plus microlenses. We find that at the typical magnifications expected for observed GW events, the fraction of**dark****matter**in the form of compact microlenses, such as primordial black holes, can be constrained to percent level. Similarly, if a small percentage of the**dark****matter**is in the form of microlenses with a few tens of solar masses, at sufficiently large magnification factors, all gravitational waves will show interference effects. These effects could have an impact on the inferred parameters. The effect is more important for macroimages with negative parity, which usually arrive after the macroimages with positive parity.9 days ago

7/10 relevant

arXiv

7/10 relevant

arXiv

Axion **Dark** **Matter**, Proton Decay and Unification

We discuss the possibility to predict the QCD axion mass in the context of grand unified theories. Expand abstract.

We discuss the possibility to predict the QCD axion mass in the context of grand unified theories. We investigate the implementation of the DFSZ mechanism in the context of renormalizable SU(5) theories. In the simplest theory, the axion mass can be predicted with good precision in the range $m_a = (2-16)$ neV, and there is a strong correlation between the predictions for the axion mass and proton decay rates. In this context, we predict an upper bound for the proton decay channels with antineutrinos, $\tau(p\to K^+ \bar{\nu}) \lesssim 4 \times 10^{37} \text{ yr}$ and $\tau(p \to \pi^+ \bar{\nu}) \lesssim 2 \times 10^{36}\text{ yr}$. This theory can be considered as the minimal realistic grand unified theory with the DFSZ mechanism and it can be fully tested by proton decay and axion experiments.

9 days ago

7/10 relevant

arXiv

7/10 relevant

arXiv

The **Dark** **Matter** Distributions in Low-Mass Disk Galaxies. II. The Inner
Density Profiles

Dark matter-only simulations predict that dark matter halos have steep, cuspy inner density profiles, while observations of dwarf galaxies find a range of inner slopes that are often much shallower. Expand abstract.

**Dark**

**matter**-only simulations predict that

**dark**

**matter**halos have steep, cuspy inner density profiles, while observations of dwarf galaxies find a range of inner slopes that are often much shallower. There is debate whether this discrepancy can be explained by baryonic feedback or if it may require modified

**dark**

**matter**models. In Paper 1 of this series, we obtained high-resolution integral field H$\alpha$ observations for 26 dwarf galaxies with $M_*=10^{8.1}-10^{9.7}\textrm{M}_\odot$. We derived rotation curves from our observations, which we use here to construct mass models. We model the total mass distribution as the sum of a generalized Navarro-Frenk-White (NFW)

**dark**

**matter**halo and the stellar and gaseous components. Our analysis of the slope of the

**dark**

**matter**density profile focuses on the inner 300-800 pc, chosen based on the resolution of our data and the region resolved by modern hydrodynamical simulations. The inner slope measured using ionized and molecular gas tracers is consistent, and it is additionally robust to the choice of stellar mass-to-light ratio. We find a range of

**dark**

**matter**profiles, including both cored and cuspy slopes, with an average of $\rho_{\rm DM}\sim r^{-0.74\pm 0.07}$, shallower than the NFW profile, but steeper than those typically observed for lower-mass galaxies with $M_*\sim 10^{7.5}\textrm{M}_\odot$. Simulations that reproduce the observed slopes in those lower-mass galaxies also produce slopes that are too shallow for galaxies in our mass range. We therefore conclude that supernova feedback models do not yet provide a fully satisfactory explanation for the observed trend in

**dark**

**matter**slopes.

9 days ago

10/10 relevant

arXiv

10/10 relevant

arXiv

DANCE: **Dark** **matter** Axion search with riNg Cavity Experiment

We have proposed a new approach to search for axion dark matter with an optical ring cavity [Phys. Expand abstract.

We have proposed a new approach to search for axion

**dark****matter**with an optical ring cavity [Phys. Rev. Lett. 121, 161301 (2018)]. The coupling of photons to axions or axion-like particles makes a modulated difference in the phase velocity between left- and right-handed photons. Our method is to measure this phase velocity difference with a ring cavity, by measuring the resonant frequency difference between two circular polarizations. Our estimation shows that the sensitivity to axion-photon coupling constant $g_{a \gamma}$ for axion mass $m \lesssim 10^{-10}$ eV can be improved by several orders of magnitude compared with the current best limits. In this paper, we present the principles of the**Dark****matter**Axion search with riNg Cavity Experiment (DANCE) and the status of the prototype experiment, DANCE Act-1.11 days ago

10/10 relevant

arXiv

10/10 relevant

arXiv

Improved limits on solar axions and bosonic **dark** **matter** from the CDEX-1B
experiment using profile likelihood ratio method

We present improved constraints on couplings of solar axions and more generic bosonic dark matter particles using 737.1 kg-days of data from the CDEX-1B experiment. Expand abstract.

We present improved constraints on couplings of solar axions and more generic bosonic

**dark****matter**particles using 737.1 kg-days of data from the CDEX-1B experiment. The CDEX-1B experiment, located at the China Jinping Underground Laboratory, primarily aims at the direct detection of WIMPs using a p-type point-contact germanium detector. We develop the profile likelihood ratio method for analysis of data in the presence of backgrounds. The background modeling is compatible with the data and no excess signals are observed. An energy threshold of 160 eV was achieved. This significantly improve the sensitivity for the bosonic**dark****matter**below 0.8 keV. Limits are also placed on the coupling $g_{Ae} < 2.26 \times 10^{-11}$ from Compton, bremsstrahlung, atomic-recombination and de-excitation channels and $g^{eff}_{AN} \times g_{Ae} < 4.14 \times 10^{-17}$ from a $^{57}$Fe M1 transition at 90\% confidence level. All the constrains improve over our previous results.14 days ago

10/10 relevant

arXiv

10/10 relevant

arXiv