1,721,390 research outputs found
Cosmological models with multiple dark matter species and long-range scalar interactions
No full textIn this talk, I have discussed the implications of a multi-component nature
of cosmic Dark Matter for the observational bounds on possible long-range
fifth-forces mediated by a Dark Energy scalar field. By assuming a simple
internal symmetry of the Dark Matter component associated to opposite coupling
"charges" of two different particle species, the effects of Dark Energy
interactions on both the background and linear perturbations evolution are
strongly suppressed during the whole matter dominated phase, thereby relaxing
present bounds on the coupling strength. The associated attractive and
repulsive fifth-forces, however, might still have a very significant impact on
the nonlinear dynamics of collapsed structures. I have also described how some
of these nonlinear effects are identified through dedicated cosmological N-body
simulations as i) a possible fragmentation of bound Dark Matter halos into
smaller objects, and ii) a consequent suppression of the nonlinear matter power
at small scales. Both effects are potentially observable and might allow to
further constrain the model
QC-LDPC code-based cryptography
No full textThis book describes the fundamentals of cryptographic primitives based on quasi-cyclic low-density parity-check (QC-LDPC) codes, with a special focus on the use of these codes in public-key cryptosystems derived from the McEliece and Niederreiter schemes. In the first part of the book, the main characteristics of QC-LDPC codes are reviewed, and several techniques for their design are presented, while tools for assessing the error correction performance of these codes are also described. Some families of QC-LDPC codes that are best suited for use in cryptography are also presented. The second part of the book focuses on the McEliece and Niederreiter cryptosystems, both in their original forms and in some subsequent variants. The applicability of QC-LDPC codes in these frameworks is investigated by means of theoretical analyses and numerical tools, in order to assess their benefits and drawbacks in terms of system efficiency and security. Several examples of QC-LDPC code-based public key cryptosystems are presented, and their advantages over classical solutions are highlighted. The possibility of also using QC-LDPC codes in symmetric encryption schemes and digital signature algorithms is also briefly examined
On the Usage of LDPC Codes in the McEliece Cryptosystem
No full textRiunione Annuale GTTI 2007 - Sessione su Tecnologie Trasmissiv
The nonlinear evolution of large scale structures in Growing Neutrino cosmologies
No full textWe present the results of the first N-body simulations of the Growing
Neutrino scenario, as recently discussed in Baldi et al. (2011). Our results
have shown for the first time how neutrino lumps forming in the context of
Growing Neutrino cosmologies are expected to pulsate as a consequence of the
rapid oscillations of the dark energy scalar field. We have also computed for
the first time a realistic statistical distribution of neutrino halos and
determined their impact on the underlying Cold Dark Matter structures
The CIDER simulations: Nonlinear structure formation in the Constrained Interacting Dark Energy Scenario
Full text linkWe present for the first time a suite of cosmological simulations for a
particular class of interacting Dark Energy cosmologies characterised by a
background expansion history constrained to be indistinguishable from CDM. Such Constrained Interacting Dark Energy scenario -- or CIDER -- has been
recently proposed by Barros et al. 2019 and has the appealing feature of
suppressing structure formation at late times, thereby possibly alleviating the
persisting tension while leaving background observables
unaffected. A crucial step to assess the viability of such scenarios is then
represented by quantifying their impact on structure formation at non-linear
scales, which is what we start investigating with the simulations discussed in
the present work. We show that -- for reasonable parameter choices -- the
reconstructed scalar potential is close to an exponential for most of the
matter dominated epoch, and that the nonlinear evolution of structures in these
models imprints specific footprints on matter and halo statistics that may
allow to break degeneracies with standard cosmological parameters.Comment: 18 pages, 12 figures, 2 tables. Sumbitted to MNRA
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