3,535 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
Automating defects simulation and fault modeling for SRAMs
The continues improvement in manufacturing process density for very deep sub micron technologies constantly leads to new classes of defects in memory devices. Exploring the effect of fabrication defects in future technologies, and identifying new classes of realistic functional fault models with their corresponding test sequences, is a time consuming task up to now mainly performed by hand. This paper proposes a new approach to automate this procedure. The proposed method exploits the capabilities of evolutionary algorithms to automatically identify faulty behaviors into defective memories and to define the corresponding fault models and relevant test sequences. Target defects are modeled at the electrical level in order to optimize the results to the specific technology and memory architecture
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
Mosaic multi-state scenario vs. one-state description of supercooled liquids
According to the mosaic scenario, relaxation in supercooled liquids is ruled
by two competing mechanisms: surface tension, opposing the creation of local
excitations, and entropy, providing the drive to the configurational
rearrangement of a given region. We test this scenario through numerical
simulations well below the Mode Coupling temperature. For an equilibrated
configuration, we freeze all the particles outside a sphere and study the
thermodynamics of this sphere. The frozen environment acts as a pinning field.
Measuring the overlap between the unpinned and pinned equilibrium
configurations of the sphere, we can see whether it has switched to a different
state. We do not find any clear evidence of the mosaic scenario. Rather, our
results seem compatible with the existence of a single (liquid) state. However,
we find evidence of a growing static correlation length, apparently unrelated
to the mosaic one.Comment: 4 pages, 3 figures, final version accepted in PR
Functional Testing Approaches for "BIFST-able" tlm_fifo
Evolution of Electronic System Level design methodologies, allows a wider use of Transaction-Level Modeling (TLM). TLM is a high-level approach to modeling digital systems that emphasizes on separating communications among modules from the details of functional units. This paper explores different functional testing approaches for the implementation of Built-in Functional Self Test facilities in the TLM primitive channel tlm_fifo. In particular, it focuses on three different test approaches based on a finite state machine model of tlm_fifo, functional fault models, and march tests respectivel
Plug & Test at System Level via Testable TLM Primitives
With the evolution of Electronic System Level (ESL) design methodologies, we are experiencing an extensive use of Transaction-Level Modeling (TLM). TLM is a high-level approach to modeling digital systems where details of the communication among modules are separated from the those of the implementation of functional units. This paper represents a first step toward the automatic insertion of testing capabilities at the transaction level by definition of testable TLM primitives. The use of testable TLM primitives should help designers to easily get testable transaction level descriptions implementing what we call a "Plug & Test" design methodology. The proposed approach is intended to work both with hardware and software implementations. In particular, in this paper we will focus on the design of a testable FIFO communication channel to show how designers are given the freedom of trading-off complexity, testability levels, and cos
Analysis of System-Failure Rate Caused by Soft-Errors using a UML-Based Systematic Methodology in an SoC
This paper proposes an analytical method to assess the soft-error rate (SER) in the early stages of a System-on-Chip (SoC) platform-based design methodology. The proposed method gets an executable UML (Unified Modeling Language) model of the SoC and the raw soft- error rate of different parts of the platform as its inputs. Soft-errors on the design are modeled by disturbances on the value of attributes in the classes of the UML model and disturbances on opcodes of software cores. The Dynamic behavior of each core is used to determine the propagation probability of each variable disturbance to the core outputs. Furthermore, the SER and the execution time of each core in the SoC and a Failure Modes and Effects Analysis (FMEA) that determines the severity of each failure mode in the SoC are used to compute the System-Failure Rate (SFR) of the So
Two-Point Versus Multipartite Entanglement in Quantum Phase Transitions
We analyze correlations between subsystems for an extended Hubbard model
exactly solvable in one dimension, which exhibits a rich structure of quantum
phase transitions (QPTs). The T=0 phase diagram is exactly reproduced by
studying singularities of single-site entanglement. It is shown how comparison
of the latter quantity and quantum mutual information allows one to recognize
whether two-point or shared quantum correlations are responsible for each of
the occurring QPTs. The method works in principle for any number D of degrees
of freedom per site. As a by-product, we are providing a benchmark for direct
measures of bipartite entanglement; in particular, here we discuss the role of
negativity at the transition.Comment: 4 pages, 2 figures, 1 tabl
Knock-Out of the Genes Coding for the Rieske Protein and the ATP-Synthase δ-Subunit of Arabidopsis
In Arabidopsis, the nuclear genes PetC and AtpD code for the Rieske protein of the cytochrome b6/f (cyt b6/f) complex and the δ-subunit of the chloroplast ATP synthase (cpATPase), respectively. Knock-out alleles for each of these loci have been identified. Greenhouse-grown petc-2 and atpd-1 mutants are seedling lethal, whereas heterotrophically propagated plants display a high-chlorophyll (Chl)-fluorescence phenotype, indicating that the products of PetC and AtpD are essential for photosynthesis. Additional effects of the mutations in axenic culture include altered leaf coloration and increased photosensitivity. Lack of the Rieske protein affects the stability of cyt b6/f and influences the level of other thylakoid proteins, particularly those of photosystem II. In petc-2, linear electron flow is blocked, leading to an altered redox state of both the primary quinone acceptor QA in photosystem II and the reaction center Chl P700 in photosystem I. Absence of cpATPase-δ destabilizes the entire cpATPase complex, whereas residual accumulation of cyt b6/f and of the photosystems still allows linear electron flow. In atpd-1, the increase in non-photochemical quenching of Chl fluorescence and a higher de-epoxidation state of xanthophyll cycle pigments under low light is compatible with a slower dissipation of the transthylakoid proton gradient. Further and clear differences between the two mutations are evident when mRNA expression profiles of nucleus-encoded chloroplast proteins are considered, suggesting that the physiological states conditioned by the two mutations trigger different modes of plastid signaling and nuclear response
Health Care Financing Reforms in Italy: Projects of Jefferson\u27s Center for Research in Medical Education and Health Care
No abstract available
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