77,364 research outputs found
Cosmology with mirror dark matter II: Cosmic Microwave Background and Large Scale Structure
This is the second paper of a series devoted to the study of the cosmological
implications of the existence of mirror dark matter. The parallel hidden mirror
world has the same microphysics as the observable one and couples the latter
only gravitationally. The primordial nucleosynthesis bounds demand that the
mirror sector should have a smaller temperature T' than the ordinary one T, and
by this reason its evolution can be substantially deviated from the standard
cosmology. In this paper we took scalar adiabatic perturbations as the input in
a flat Universe, and computed the power spectra for ordinary and mirror CMB and
LSS, changing the cosmological parameters, and always comparing with the CDM
case. We found differences in both the CMB and LSS power spectra, and we
demonstrated that the LSS spectrum is particularly sensitive to the mirror
parameters, due to the presence of both the oscillatory features of mirror
baryons and the collisional mirror Silk damping. For x<0.3 the mirror
baryon-photon decoupling happens before the matter-radiation equality, so that
CMB and LSS power spectra in linear regime are equivalent for mirror and CDM
cases. For higher x-values the LSS spectra strongly depend on the amount of
mirror baryons. Finally, qualitatively comparing with the present observational
limits on the CMB and LSS spectra, we show that for x<0.3 the entire dark
matter could be made of mirror baryons, while in the case x>0.3 the pattern of
the LSS power spectrum excludes the possibility of dark matter consisting
entirely of mirror baryons, but they could present as admixture (up to 50%) to
the conventional CDM.Comment: 36 pages, 19 figures; minor corrections in introduction, conclusions
and references; accepted for publication in IJMP
Entanglement entropy with localized and extended interface defects
The quantum Ising chain of length, L, which is separated into two parts by
localized or extended defects is considered at the critical point where scaling
of the interface magnetization is non-universal. We measure the entanglement
entropy between the two halves of the system in equilibrium, as well as after a
quench, when the interaction at the interface is changed for time t>0. For the
localized defect the increase of the entropy with log(L) or with log(t)
involves the same effective central charge, which is a continuous function of
the strength of the defect. On the contrary for the extended defect the
equilibrium entropy is saturated, but the non-equilibrium entropy has a
logarithmic time-dependence the prefactor of which depends on the strength of
the defect.Comment: 9 pages, 6 figure
Cosmology with mirror dark matter I: linear evolution of perturbations
This is the first paper of a series devoted to the study of the cosmological
implications of the parallel mirror world with the same microphysics as the
ordinary one, but having smaller temperature, with a limit set by the BBN
constraints. The difference in temperature of the ordinary and mirror sectors
generates shifts in the key epochs for structure formation, which proceeds in
the mirror sector under different conditions. We consider adiabatic scalar
primordial perturbations as an input and analyze the trends of all the relevant
scales for structure formation (Jeans length and mass, Silk scale, horizon
scale) for both ordinary and mirror sectors, comparing them with the CDM case.
These scales are functions of the fundamental parameters of the theory (the
temperature of the mirror plasma and the amount of mirror baryonic matter), and
in particular they are influenced by the difference between the cosmological
key epochs in the two sectors. Then we used a numerical code to compute the
evolution in linear regime of density perturbations for all the components of a
Mirror Universe: ordinary baryons and photons, mirror baryons and photons, and
possibly cold dark matter. We analyzed the evolution of the perturbations for
different values of mirror temperature and baryonic density, and obtained that
for x=T'/T less than a typical value x_eq, for which the mirror baryon-photon
decoupling happens before the matter-radiation equality, mirror baryons are
equivalent to the CDM for the linear structure formation process. Indeed, the
smaller the value of x, the closer mirror dark matter resembles standard cold
dark matter during the linear regime.Comment: 33 pages, 24 figures; minor corrections in introduction, conclusions
and references; accepted for publication in IJMP
Particle-Level Modeling of the Charge-Discharge Behavior of Nanoparticulate Phase-Separating Li-Ion Battery Electrodes
In nanoparticulate phase-separating electrodes, phase separation inside the
particles can be hindered during their charge/discharge cycles even when a
thermodynamic driving force for phase separation exists. In such cases,
particles may (de)lithiate discretely in a process referred to as mosaic
instability. This instability could be the key to elucidating the complex
charge/discharge dynamics in nanoparticulate phase-separating electrodes. In
this paper, the dynamics of the mosaic instability is studied using Smoothed
Boundary Method simulations at the particle level, where the concentration and
electrostatic potential fields are spatially resolved around individual
particles. Two sets of configurations consisting of spherical particles with an
identical radius are employed to study the instability in detail. The effect of
an activity-dependent exchange current density on the mosaic instability, which
leads to asymmetric charge/discharge, is also studied. While we show that our
model reproduces the results of a porous-electrode model for the simple setup
studied here, it is a powerful framework with the capability to predict the
detailed dynamics in three-dimensional complex electrodes and provides further
insights into the complex dynamics that result from the coupling of
electrochemistry, thermodynamics, and transport kinetics
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