Subdynamics of relevant observables: a field theoretical approach

An approach to the description of subdynamics inside non-relativistic quantum field theory is presented, in which the notions of relevant observable, time scale and complete positivity of the time evolution are stressed. A scattering theory derivation of the subdynamics of a microsystem interacting through collisions with a macrosystem is given, leading to a master-equation expressed in terms of the operator-valued dynamic structure factor, a two-point correlation function which compactly takes the statistical mechanics properties of the macrosystem into account. For the case of a free quantum gas the dynamic structure factor can be exactly calculated and in the long wavelength limit a Fokker-Planck equation for the description of quantum dissipation and in particular quantum Brownian motion is obtained, where peculiar corrections due to quantum statistics can be put into evidence.Comment: 28 pages, latex, no figure

Translation-covariant Markovian master equation for a test particle in a quantum fluid

A recently proposed master equation in the Lindblad form is studied with respect to covariance properties and existence of a stationary solution. The master equation describes the interaction of a test particle with a quantum fluid, the so-called Rayleigh gas, and is characterized by the appearance of a two-point correlation function known as dynamic structure factor, which reflects symmetry and statistical mechanics properties of the fluid. In the case of a free gas all relevant physical parameters, such as fugacity, ratio between the masses, momentum transfer and energy transfer are put into evidence, giving an exact expansion of the dynamic structure factor. The limit in which these quantities are small is then considered. In particular in the Brownian limit a Fokker-Planck equation is obtained in which the corrections due to quantum statistics can be explicitly evaluated and are given in terms of the Bose function $g_0 (z)$ and the Fermi function $f_0 (z)$.Comment: 18 pages, revtex, no figures, to appear in J. Math. Phy

A classical appraisal of quantum definitions of non-Markovian dynamics

We consider the issue of non-Markovianity of a quantum dynamics starting from a comparison with the classical definition of Markovian process. We point to the fact that two sufficient but not necessary signatures of non-Markovianity of a classical process find their natural quantum counterpart in recently introduced measures of quantum non-Markovianity. This behavior is analyzed in detail for quantum dynamics which can be built taking as input a class of classical processes.Comment: 15 pages, 6 figures; to appear in J. Phys. B, Special Issue on "Loss of coherence and memory effects in quantum dynamics

Subdynamics as a mechanism for objective description

The relationship between microsystems and macrosystems is considered in the context of quantum field formulation of statistical mechanics: it is argued that problems on foundations of quantum mechanics can be solved relying on this relationship. This discussion requires some improvement of non-equilibrium statistical mechanics that is briefly presented.Comment: latex, 15 pages. Paper submitted to Proc. Conference "Mysteries, Puzzles And Paradoxes In Quantum Mechanics, Workshop on Entanglement And Decoherence, Palazzo Feltrinelli, Gargnano, Garda Lake, Italy, 20-25 September, 199

Non-Markovian dynamics for bipartite systems

We analyze the appearance of non-Markovian effects in the dynamics of a bipartite system coupled to a reservoir, which can be described within a class of non-Markovian equations given by a generalized Lindblad structure. A novel master equation, which we term quantum Bloch-Boltzmann equation, is derived, describing both motional and internal states of a test particle in a quantum framework. When due to the preparation of the system or to decoherence effects one of the two degrees of freedom is amenable to a classical treatment and not resolved in the final measurement, though relevant for the interaction with the reservoir, non-Markovian behaviors such as stretched exponential or power law decay of coherences can be put into evidence.Comment: published version, 15 pages, revtex, no figure

Misura dei cambiamenti paesaggistici in ambiente alpino attraverso l’integrazione di dati telerilevati

Dalla met\ue0 del secolo scorso il paesaggio italiano ha subito delle profonde trasformazioni dovute al cambiamento di uso/copertura del suolo con la perdita di prati e pascoli a causa dei naturali processi di successione forestale, con forti ripercussioni sulla conservazione della biodiversit\ue0 (Falcucci et al. 2006). Gli ecosistemi alpini sono particolarmente sensibili a queste modifiche (Gehrig-Fasel et al. 2007) a causa dell\u2019elevato grado di endemismi fortemente adattati (Billings 1974). Per attuare delle misure di tipo conservazionistico, quindi \ue8 fondamentale quantificare il cambiamento di copertura del suolo avvenuto negli ultimi decenni ed impostare un monitoraggio a lungo termine delle strutture vegetali per individuare le aree maggiormente sensibili

Reply to Comment on "Completely positive quantum dissipation"

This is the reply to a Comment by R. F. O'Connell (Phys. Rev. Lett. 87 (2001) 028901) on a paper written by the author (B. Vacchini, ``Completely positive quantum dissipation'', Phys.Rev.Lett. 84 (2000) 1374, arXiv:quant-ph/0002094).Comment: 2 pages, revtex, no figure

Patterns of spatio-temporal change in Alpine ibex (Capra ibex ibex, L.) distribution in Gran Paradiso National Park

Ibex is the symbolic species of mountain ungulates and currently it is classified at Least Concern by IUCN. In the last few decades there was a drastic decrease in population abundance linked with a reduction of stable occupied territories. Causes are still not completely clear but drastic decline is in partly due to recent climate changes. The objectives of this study are to analyse the ibex distribution changes in Gran Paradiso National Park (GPNP) in 1985-2014 period, the type of relation between pattern of distribution and population trend and finally the evidence of most used ibex \u2018s territories in GPNP. To understand distribution patterns ibex census data are been analysed using metrics belonging to landscape ecology, an approach based on the notion that environmental patterns influence ecological processes. In particular 5 metrics are been used to assess the composition and spatial configuration of occupied areas, while distribution statistics provided a statistical summaries of obtained results. Results showed a reduction of ibex occupied territories from 4587.50 ha in 1985 to 2437.50 ha in 2014 and fragmentation of ibex occupied territories with a strong increase in number of occupied patches from 130 units to 229 units. We suggest that likely ibex distribution was influenced by different combined factors (landscape change, climate change, anthropic activities), which have to be still examined in depth. Landscape ecology approach may become an useful tool to understand the degree of fragmentation and connectivity of landscape defined on species distribution. The understanding of processes behind Alpine ungulates distribution have to consider the influence of landscape patterns on environmental processes to improve the conservation efforts at management level

Reproductive payoffs of territoriality are snow-dependent in a mountain ungulate, the Alpine chamois

Female density and distribution are dependent on resource phenology and female availability strongly influences male mating behaviour and success. When a male adopts a ‘resource defence’ tactic, his reproductive success depends on the location and attractiveness of his territory. Environmental factors associated with territory quality are expected to influence mating success, for example, through territory features or male–male competition. In a protected population of a mountain-dwelling polygynous herbivore, the Alpine chamois Rupicapra r. rupicapra, we investigated the relationships among mating opportunities, some environmental variables (snow depth, topographic features and size of territories) and male intra-sexual competition for mating. We recorded the mating behaviour and territory size of 15 GPS-GSM radio-tagged territorial males, during five rutting seasons (early November to early December: N = 8 individuals in 2011, N = 9 in 2012, N = 8 in 2015, N = 11 in 2016, N = 7 in 2017; 80% of them were observed for more than one mating season) and related them to snow depth and topography of territories. In ruts with deep snow cover, territorial males had smaller territories and higher number of mating opportunities than in ruts with lower snow cover. Smaller territories showed the highest values of terrain roughness, in turn with little or no snow cover in the mating season, and were visited by a greater number of females, than larger territories. Number of wins was positively influenced by snow depth and negatively related to the frequency of aggressions. The frequency of male–male aggressive interactions was greater during ruts with deep snow cover and for males with territories at higher elevations; additionally, it was negatively related to interactions won. Thus, snow depth, which influences resource distribution and female movements, is confirmed as a strong determinant of male mating opportunities and mating behaviour

Quantum optical versus quantum Brownian motion master-equation in terms of covariance and equilibrium properties

Structures of quantum Fokker-Planck equations are characterized with respect to the properties of complete positivity, covariance under symmetry transformations and satisfaction of equipartition, referring to recent mathematical work on structures of unbounded generators of covariant quantum dynamical semigroups. In particular the quantum optical master-equation and the quantum Brownian motion master-equation are shown to be associated to $\mathrm{U(1)}$ and $\mathrm{R}$ symmetry respectively. Considering the motion of a Brownian particle, where the expression of the quantum Fokker-Planck equation is not completely fixed by the aforementioned requirements, a recently introduced microphysical kinetic model is briefly recalled, where a quantum generalization of the linear Boltzmann equation in the small energy and momentum transfer limit straightforwardly leads to quantum Brownian motion.Comment: 11 pages, latex, no figures, slight changes and a few references added, to appear in J. Math. Phy