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Search Results: 1 - 10 of 5704 matches for " Vera Guarrera "
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Localization by Dissipative Disorder: a Deterministic Approach to Position Measurements
Giovanni Barontini,Vera Guarrera
Physics , 2015, DOI: 10.1103/PhysRevA.91.032114
Abstract: We propose an approach to position measurements based on the hypothesis that the action of a position detector on a quantum system can be effectively described by a dissipative disordered potential. We show that such kind of potential is able, via the dissipation-induced Anderson localization, to contemporary localize the wavefunction of the system and to dissipate information to modes bounded to the detector. By imposing a diabaticity condition we demonstrate that the dissipative dynamics between the modes of the system leads to a localized energy exchange between the detector and the rest of the environment -the "click" of the detector- thus providing a complete deterministic description of a position measurement. We finally numerically demonstrate that our approach is consistent with the Born probability rule.
A cold-atom random laser
Quentin Baudouin,Nicolas Mercadier,Vera Guarrera,William Guerin,Robin Kaiser
Physics , 2013, DOI: 10.1038/nphys2614
Abstract: Conventional lasers make use of optical cavities to provide feedback to gain media. Conversely, mirrorless lasers can be built by using disordered structures to induce multiple scattering, which increases the effective path length in the gain medium and thus provides the necessary feedback. These so-called random lasers potentially offer a new and simple mean to address applications such as lighting. To date, they are all based on condensed-matter media. Interestingly, light or microwave amplification by stimulated emission occurs also naturally in stellar gases and planetary atmospheres. The possibility of additional scattering-induced feedback (that is, random lasing) has been discussed and could explain unusual properties of some space masers. Here, we report the experimental observation of random lasing in a controlled, cold atomic vapour, taking advantage of Raman gain. By tuning the gain frequency in the vicinity of a scattering resonance, we observe an enhancement of the light emission of the cloud due to random lasing. The unique possibility to both control the experimental parameters and to model the microscopic response of our system provides an ideal test bench for better understanding natural lasing sources, in particular the role of resonant scattering feedback in astrophysical lasers.
Cross-dimensional phase transition from an array of 1D Luttinger liquids to a 3D Bose-Einstein condensate
Andreas Vogler,Ralf Labouvie,Giovanni Barontini,Sebastian Eggert,Vera Guarrera,Herwig Ott
Physics , 2014, DOI: 10.1103/PhysRevLett.113.215301
Abstract: We study the thermodynamic properties of a 2D array of coupled one-dimensional Bose gases. The system is realized with ultracold bosonic atoms loaded in the potential tubes of a two-dimensional optical lattice. For negligible coupling strength, each tube is an independent weakly interacting 1D Bose gas featuring Tomonaga Luttinger liquid behavior. By decreasing the lattice depth, we increase the coupling strength between the 1D gases and allow for the phase transition into a 3D condensate. We extract the phase diagram for such a system and compare our results with theoretical predictions. Due to the high effective mass across the periodic potential and the increased 1D interaction strength, the phase transition is shifted to large positive values of the chemical potential. Our results are prototypical to a variety of low-dimensional systems, where the coupling between the subsystems is realized in a higher spatial dimension such as coupled spin chains in magnetic insulators.
Observation of local temporal correlations in trapped quantum gases
Vera Guarrera,Peter Wuertz,Arne Ewerbeck,Andreas Vogler,Giovanni Barontini,Herwig Ott
Physics , 2011, DOI: 10.1103/PhysRevLett.107.160403
Abstract: We measure the temporal pair correlation function $g^{(2)}(\tau)$ of a trapped gas of bosons above and below the critical temperature for Bose-Einstein condensation. The measurement is performed {\it in situ} using a local, time-resolved single-atom sensitive probing technique. Third and fourth order correlation functions are also extracted. We develop a theoretical model and compare it with our experimental data, finding good quantitative agreement and highlighting the role of interactions. Our results promote temporal correlations as new observables to study the dynamics of ultracold quantum gases.
Thermodynamics of Strongly Correlated One-Dimensional Bose Gases
Andreas Vogler,Ralf Labouvie,Felix Stubenrauch,Giovanni Barontini,Vera Guarrera,Herwig Ott
Physics , 2013, DOI: 10.1103/PhysRevA.88.031603
Abstract: We investigate the thermodynamics of one-dimensional Bose gases in the strongly correlated regime. To this end, we prepare ensembles of independent 1D Bose gases in a two-dimensional optical lattice and perform high-resolution in situ imaging of the column-integrated density distribution. Using an inverse Abel transformation we derive e?ective one-dimensional line-density pro?les and compare them to exact theoretical models. The high resolution allows for a direct thermometry of the trapped ensembles. The knowledge about the temperature enables us to extract thermodynamic equations of state such as the phase-space density, the entropy per particle and the local pair correlation function.
Household dyeing plants and traditional uses in some areas of Italy
Paolo Guarrera
Journal of Ethnobiology and Ethnomedicine , 2006, DOI: 10.1186/1746-4269-2-9
Abstract: Twenty-nine plants are described, distributed in 23 families, and for each species the vernacular name, the way it is used and the locations of traditional use are given. Other plants used in the past in the above-mentioned regions are recalled.Among the new findings – not mentioned in previous literature, see references – is Muscari neglectum (purplish). Nowadays atavistic dye uses still persist only in Nule (Sardinia).This research into a particular field of ethno-botanical traditions – the use of household dyeing plants – was motivated by the wish to preserve the memory of customs that in centuries past expressed the close relationship farmers and shepherds had with nature.It is well known that dye substances of plant origin present in many wild and cultivated species, were the first to be used by man in this particular craft.Many plants contain in the second half of their binomial name the word "tinctorius" or its derivatives, which underlines their dyeing properties and their past use in dye-house. They range from lichens to Angiospermae Compositae like Carthamus tinctorius L. and Anthemis tinctoria L., Leguminosae such as Genista tinctoria L., Cruciferae such as Isatis tinctoria L., Boraginaceae such as Alkanna tinctoria (L.) Tausch., Rubiaceae such as Rubia tinctorum L. etc. The first or the second part of the scientific name of many plants refers to the colour imparted by their parts. The Rubia genus reminds us of the reddish colour produced by alizarin, an antraquinonic substance contained in the root, while Reseda lutea L. and Reseda luteola L. remind us of the yellowish colour obtained from the plants.The Italian names of some plants also show their dyeing properties: e.g. Centaurium erythraea Rafn. is called "biondella" because it bleaches brown hair, Rhamnus saxatilis Jacq. subsp. infectorius (L.) P. Fourn. is called "ranno dei tintori" as it contains antraquinonic dyeing substances, also present in the Rubia genus.In this paper, in order to contribute
Ethnobotanical remarks on Central and Southern Italy
Paolo Guarrera, Leporatti Lucia
Journal of Ethnobiology and Ethnomedicine , 2007, DOI: 10.1186/1746-4269-3-23
Abstract: Field data were collected through open interviews, mainly of farmers, shepherds and elderly people, born or living in these areas for a long time. Voucher specimens of collected plants are preserved in the respective herbaria of the Authors and in the herbarium of "Roma Tre" University. Important contributions have been made by several students native to the areas under consideration. A comparative analysis with local specific ethnobotanical literature was carried out.The paper reports several examples concerning human and veterinary popular medicine and in addition some anti-parasitic, nutraceutic, dye and miscellaneous uses are also described. Moreover vernacular names and toponyms are cited. Eight regions of central and southern Italy (particularly Latium, Abruzzo, Marche and Basilicata) were investigated and the data obtained are presented in 32 papers. Most of the species of ethnobotanical interest have been listed in Latium (368 species), Marche (274) and Abruzzo (203). The paper also highlights particularly interesting aspects or uses not previously described in the specific ethnobotanical literature.Phyto-therapy in central and southern Italy is nowadays practised by a few elderly people who resort to medicinal plants only for mild complaints (on the contrary food uses are still commonly practised). Nowadays therapeutic uses, unlike in the past, are less closely or not at all linked to ritual aspects. Several plants deserve to be taken into consideration not only from the anthropological or cultural point of view, but also for further phyto-chemical investigation. Our studies, as well as those of other authors, try to provide an original picture of the local ethno-biodiversity.The sudden evolution of society towards technological patterns and the increasing use of synthetic remedies, has seen a consequent erosion of a rich cultural heritage regarding popular phyto-therapy, that had developed over the centuries. In fact, from the end of XIX century onwards, p
Papapetrou Energy-Momentum Tensor for Chern-Simons Modified Gravity
David Guarrera,A. J. Hariton
Physics , 2007, DOI: 10.1103/PhysRevD.76.044011
Abstract: We construct a conserved, symmetric energy-momentum (pseudo-)tensor for Chern-Simons modified gravity, thus demonstrating that the theory is Lorentz invariant. The tensor is discussed in relation to other gravitational energy-momentum tensors and analyzed for the Schwarzschild, Reissner-Nordstrom, and FRW solutions. To our knowledge this is the first confirmation that the Reissner-Nordstrom and FRW metrics are solutions of the modified theory.
Agricultural, domestic and handicraft folk uses of plants in the Tyrrhenian sector of Basilicata (Italy)
Giovanni Salerno, Paolo Guarrera, Giulia Caneva
Journal of Ethnobiology and Ethnomedicine , 2005, DOI: 10.1186/1746-4269-1-2
Abstract: The taxa cited are 60, belonging to 32 botanical families, of which 18 are employed for agricultural uses and 51 for domestic-handicraft folk uses. Data show a diffuse use of plants for many purposes, both in agricultural (present uses 14%; past uses 1%) and for domestic-handicraft use (present uses 40%; past uses 45%); most of the latter are now in decline.60 data look uncommon or typical of the places studied. Some domestic-handicraft folk uses are typical of southern Italy (e.g. the use of Ampelodesmos mauritanicus for making ties, ropes, torches, baskets or that of Acer neapolitanum for several uses). Other uses (e.g. that of Inula viscosa and Calamintha nepeta for peculiar brooms, and of Origanum heracleoticum for dyeing wool red) are previously unpublished.Ethnobotanical studies supporting the ethno-anthropological sciences, and of "material culture", which describe aspects of farmers' and shepherds' economy now on the point of disappearance are infrequent in Italy. Generic news is sometimes present in botanical texts concerning, for example, handicraft uses, but the plant matter of single artefacts is rarely defined; this specific matter can change from place to place and can originate peculiar local artefacts. Ethnobotanical uses of plants are often lost more easily in modern civilisation, due to industrial activity that substitutes traditional handicrafts. This study was carried out in an area, the Tyrrhenian sector of Basilicata, where, in remarkable contrast with that happens in the rest of Italy, we can still witness a large folk employment of plants and a rich and intense memory of their uses is present. Due to history, economy and tradition, this area could potentially be a precious source of information already lost in other places.A previous study of flora, vegetation and spontaneous food plants [1] underlined the still low industrial and urban impact upon the area of study, considered a good source of information for ethnobotanical applications typi
Food, flavouring and feed plant traditions in the Tyrrhenian sector of Basilicata, Italy
Paolo Guarrera, Giovanni Salerno, Giulia Caneva
Journal of Ethnobiology and Ethnomedicine , 2006, DOI: 10.1186/1746-4269-2-37
Abstract: Field data were collected through structured interviews. The informants, numbered 49, belonged to families which had strong links with the traditional activities of the area.61 taxa are cited, belonging to 26 botanical families, amongst which 44 used as food or flavouring and 22 for animal alimentation. Besides 7 taxa are involved in rituals especially connected with agriculture and plant growth.The preservation of some rituals especially concerning agricultural plants is noteworthy in the area, together with a certain degree of continuity in food uses. Knowledge and rediscovery of recipes in human and animal diet could represent an economic potential for the area.The aim of this paper is to contribute to our knowledge of the food, flavouring and feed use, both past and present, of plants found throughout the Tyrrhenian part of Basilicata, an area never before fully investigated from this aspect. Some investigation was carried out in Basilicata region, concerning food and flavouring plants, while no research was made on fodder plants. Few data were reported for the Tyrrhenian coast in a book by Caneva et al. [1]; other papers, by Pieroni et al. [2-5], studied some communities of Arb?resh? in internal areas of the region.The research area is located in Potenza province, between the regions of Campania to the north and of Calabria to the south, including roughly 28 km of coastline. This territory (latitude 40°N, longitude 15°45'E) occupies an area of 105,03 km2, facing the Gulf of Policastro; it is rich in promontories rising straight from the sea and imposing mountains (max. 1505 m). The research was carried out in the territory of Maratea with some small scattered centres stretching from the coast to the slopes of Mt. S.Biagio (Massa, Brefaro, S. Caterina, Fiumicello) and in the area of Trécchina, in the interior (Fig. 1). The territory is covered above all with a Mediterranean maquis, a vegetation of sunny rocks and mixed woods. Old specimens of Olea europaea, Cera
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