Search results for "Ideal"
showing 10 items of 440 documents
Matching stages of heavy-ion collision models
2010
Heavy-ion reactions and other collective dynamical processes are frequently described by different theoretical approaches for the different stages of the process, like initial equilibration stage, intermediate locally equilibrated fluid dynamical stage, and final freeze-out stage. For the last stage, the best known is the Cooper-Frye description used to generate the phase space distribution of emitted, noninteracting particles from a fluid dynamical expansion or explosion, assuming a final ideal gas distribution, or (less frequently) an out-of-equilibrium distribution. In this work we do not want to replace the Cooper-Frye description, but rather clarify the ways of using it and how to choo…
T Violation and CPT Tests in Neutral-Meson Systems
2014
The review covers transitions between M0 and M0bar in all four systems M0 = K0, D0, B0 and Bs. These systems are ideal laboratories for studying the discrete symmetries T and CPT. The properties of time reversal T are discussed in classical and quantum mechanics. T violation in K0 K0bar transitions has been observed in 1970 independent of assuming CPT symmetry by using the Bell-steinberger unitarity relation. Improvements of this observation are reviewed including the latest results in 2013. They show with high significance that CP violation in K0 K0bar transitions is only T violation without any CPT violation. Transitions in the other three systems do not show CP violation so far and there…
Dissipation and Elliptic Flow at Relativistic Energies
2004
We compare elliptic flow evolution from ideal hydrodynamics and covariant parton transport theory, and show that, for conditions expected at RHIC, dissipation significantly reduces elliptic flow even for extreme parton cross sections and/or densities ${\ensuremath{\sigma}}_{gg}\ifmmode\times\else\texttimes\fi{}dN/d\ensuremath{\eta}(b=0)\ensuremath{\sim}45\text{ }\mathrm{m}\mathrm{b}\ifmmode\times\else\texttimes\fi{}1000$. The difference between transport and hydrodynamic elliptic flow is established rather early during the evolution of the system, but the buildup of elliptic flow is insensitive to the choice of the initial (formation or thermalization) time in both models.
Triangular flow of thermal photons from an event-by-event hydrodynamic model for2.76ATeV Pb + Pb collisions at the CERN Large Hadron Collider
2016
We calculate the triangular flow parameter $v_3$ of thermal photons from an event-by-event ideal hydrodynamic model for $0--40\%$ central collisions of Pb nuclei at $\sqrt{s_{NN}}$=2.76 TeV at LHC. $v_3$ determined with respect to the participant plane (PP) is found to be non-zero, positive and its $p_T$ dependence is qualitatively similar to the elliptic flow parameter $v_2$(PP) of thermal photons in the range $1 \le p_T \le 6$ GeV/$c$. In the range $p_T \, \le $ 3 GeV/$c$, $v_3$(PP) is found to be about $50--75\%$ of $v_2$(PP) and for $p_T \, >$ 3 GeV/$c$ the two anisotropy parameters become comparable. The local fluctuations in the initial density distribution as well as the initial glob…
Modelling systems of classical/quantum identical particles by focusing on algorithms
2012
A procedure modelling ideal classical and quantum gases is discussed. The proposed approach is mainly based on the idea that modelling and algorithm analysis can provide a deeper understanding of particularly complex physical systems. Appropriate representations and physical models able to mimic possible pseudo-mechanisms of functioning and having predictive validity are developed.
Pseudoscalar decays into lepton pairs from rational approximants
2016
The pseudoscalar decays into lepton pairs P! ‘‘ are analyzed with the machinery of Canterbury approximants, an extension of Pade approximants to bivariate functions. This framework provides an ideal model-independent approach to implement all our knowledge of the pseudoscalar transition form factors driving these decays, can be used for data analysis, and allows to include experimental data and theoretical constraints in an easy way, and determine a systematic error. We find that previous theoretical estimates for these branching ratios have underestimated their theoretical uncertainties. From our updated results, the existing experimental discrepancies for p 0 ! e + e and h! m + m channels…
Homogeneous three-dimensional Riemannian spaces
2020
The necessary and sufficient conditions for a three-dimensional Riemannian metric to admit a transitive group of isometries are obtained. These conditions are Intrinsic, Deductive, Explicit and ALgorithmic, and they offer an IDEAL labeling of these geometries. It is shown that the transitive action of the group naturally falls into an unfolding of some of the ten types in the Bianchi-Behr classification. Explicit conditions, depending on the Ricci tensor, are obtained that characterize all these types.
Dimension of the isometry group in three-dimensional Riemannian spaces
2021
The necessary and sufficient conditions for a three-dimensional Riemannian metric to admit a group of isometries of dimension $r$ acting on s-dimensional orbits are obtained. These conditions are Intrinsic, Deductive, Explicit and ALgorithmic and they offer an IDEAL labeling that improves previously known invariant studies.
Open multistate Majorana model
2019
Abstract The Majorana model in the presence of dissipation and dephasing is considered. First, it is proven that increasing the Hilbert space dimension the system becomes more and more fragile to quantum noise, whether dephasing or dissipation are mainly present. Second, it is shown that, contrary to its ideal counterpart, the dynamics related to the open Majorana model cannot be considered as the combined dynamics of a set of independent spin-1/2 models.
Influence of dissipation on the extraction of quantum states via repeated measurements
2007
A quantum system put in interaction with another one that is repeatedly measured is subject to a non-unitary dynamics, through which it is possible to extract subspaces. This key idea has been exploited to propose schemes aimed at the generation of pure quantum states (purification). All such schemes have so far been considered in the ideal situations of isolated systems. In this paper, we analyze the influence of non-negligible interactions with environment during the extraction process, with the scope of investigating the possibility of purifying the state of a system in spite of the sources of dissipation. A general framework is presented and a paradigmatic example consisting of two inte…