75 research outputs found
Irreversible decay of nonlocal entanglement via a reservoir of a single degree of freedom
Recently, it has been realized that nonlocal disentanglement may take a
finite time as opposite to the asymptotic decay of local coherences. We find in
this paper that a sudden irreversible death of entanglement takes place in a
two atom optical Stern-Gerlach model. In particular, the one degree non
dissipative environment here considered suddenly destroys the initial
entanglement of any Bell's states superposition.Comment: 6 pages, 4 figures, improved presentation, v2: title changed,
references added, accepted for publication in Phys. Rev. A (Fundamental
concepts
Translational dynamics effects on the non-local correlations between two atoms
A pair of atoms interacting successively with the field of the same cavity
and exchanging a single photon, leave the cavity in an entangled state of
Einstein-Podolsky-Rosen (EPR) type (see, for example, [S.J.D. Phoenix, and S.M.
Barnett, J. Mod. Opt. \textbf{40} (1993) 979]). By implementing the model with
the translational degrees of freedom, we show in this letter that the
entanglement with the translational atomic variables can lead, under
appropriate conditions, towards the separability of the internal variables of
the two atoms. This implies that the translational dynamics can lead, in some
cases, to difficulties in observing the Bell's inequality violation for massive
particles.Comment: 5 pages, 1 figur
On the observability of Bell's inequality violation in the optical Stern-Gerlach model
Using the optical Stern-Gerlach model, we have recently shown that the
non-local correlations between the internal variables of two atoms that
successively interact with the field of an ideal cavity in proximity of a nodal
region are affected by the atomic translational dynamics. As a consequence,
there can be some difficulties in observing violation of the Bell's inequality
for the atomic internal variables. These difficulties persist even if the atoms
travel an antinodal region, except when the spatial wave packets are exactly
centered in an antinodal point.Comment: 5 pages, 1 figure, submitted to European Physical Journal
The non dissipative damping of the Rabi oscillations as a "which-path" information
Rabi oscillations may be viewed as an interference phenomenon due to a
coherent superposition of different quantum paths, like in the Young's two-slit
experiment. The inclusion of the atomic external variables causes a non
dissipative damping of the Rabi oscillations. More generally, the atomic
translational dynamics induces damping in the correlation functions which
describe non classical behaviors of the field and internal atomic variables,
leading to the separability of these two subsystems. We discuss on the
possibility of interpreting this intrinsic decoherence as a "which-way"
information effect and we apply to this case a quantitative analysis of the
complementarity relation as introduced by Englert [Phys. Rev. Lett.
\textbf{77}, 2154 (1996)].Comment: 5 pages, 2 figure
Scaling laws of strategic behaviour and size heterogeneity in agent dynamics
The dynamics of many socioeconomic systems is determined by the decision
making process of agents. The decision process depends on agent's
characteristics, such as preferences, risk aversion, behavioral biases, etc..
In addition, in some systems the size of agents can be highly heterogeneous
leading to very different impacts of agents on the system dynamics. The large
size of some agents poses challenging problems to agents who want to control
their impact, either by forcing the system in a given direction or by hiding
their intentionality. Here we consider the financial market as a model system,
and we study empirically how agents strategically adjust the properties of
large orders in order to meet their preference and minimize their impact. We
quantify this strategic behavior by detecting scaling relations of allometric
nature between the variables characterizing the trading activity of different
institutions. We observe power law distributions in the investment time
horizon, in the number of transactions needed to execute a large order and in
the traded value exchanged by large institutions and we show that heterogeneity
of agents is a key ingredient for the emergence of some aggregate properties
characterizing this complex system.Comment: 6 pages, 3 figure
Quantum erasure within the Optical Stern-Gerlach Model
In the optical Stern-Gerlach effect the two branches in which the incoming
atomic packet splits up can display interference pattern outside the cavity
when a field measurement is made which erases the which-way information on the
quantum paths the system can follow. On the contrary, the mere possibility to
acquire this information causes a decoherence effect which cancels out the
interference pattern. A phase space analysis is also carried out to investigate
on the negativity of the Wigner function and on the connection between its
covariance matrix and the distinguishability of the quantum paths.Comment: 7 pages, 3 figure
Thymus richardii subsp. nitidus (Guss.) Jalas Essential Oil: An Ally against Oral Pathogens and Mouth Health
The genus Thymus L., belonging to the Lamiaceae family, contains about 220 species with a distribution that mainly extends in Europe, northwest Africa, Ethiopia, Asia, and southern Greenland. Due to their excellent biological properties, fresh and/or dried leaves and aerial parts of several Thymus ssp. have been utilized in the traditional medicine of many countries. To evaluate not only the chemical aspects but also the biological properties, the essential oils (EOs), obtained from the pre-flowering and flowering aerial parts of Thymus richardii subsp. nitidus (Guss.) Jalas, endemic to Marettimo Island (Sicily, Italy), were investigated. The chemical composition of the EOs, obtained by classical hydrodistillation and GC-MS and GC-FID analyses, showed the occurrence of similar amounts of monoterpene hydrocarbons, oxygenated monoterpenes, and sesquiterpene hydrocarbons. The main constituents of the pre-flowering oil were β-bisabolene (28.54%), p-cymene (24.45%), and thymol methyl ether (15.90%). The EO obtained from the flowering aerial parts showed as principal metabolites β-bisabolene (17.91%), thymol (16.26%), and limonene (15.59%). The EO of the flowering aerial parts, and its main pure constituents, β-bisabolene, thymol, limonene, p-cymene, and thymol methyl ether were investigated for their antimicrobial activity against oral pathogens and for their antibiofilm and antioxidant properties
Uncommon localizations of hydatid cyst. Review of the literature
Introduction. Hydatid disease is an endemic anthropozoonosis with usual localization in liver and lungs. Rarely it localizes in uncommon sites as spleen, skeleton, kidney, brain, cardiac muscle, peritoneum, sub cutis. Complications of uncommon localizations are the same that for usual ones. Material and methods. Review of the literature on rare and atypical localization of hydatid cysts in soft tissues. Key-words used on Pub-Med [(echinococ OR hydatid) AND (soft tissue OR subcutaneous OR cutaneous)] without time limit. There were found 282 articles; 242 were excluded because of muscular or bone localizations. 40 were coherent. Results. Different variables are taken into account: age, sex, geographic area, anatomic localization of the cyst, dimension, symptoms, signs, mobility, blood exams and specific serological tests, imaging techniques for diagnosis, existing of septa in the structure, treatment, anaesthesia, spillage, neo-adjuvant and adjuvant treatment, follow-up period, recurrent lesions. Conclusion. It would be useful create an homogeneous and standardized collection of data of these rare and potentially life-threatening conditions in order to create guide-line of diagnostic and therapeutic process and create (or adopt) unique classification of the lesions
Market Impact and Trading Protocols of Hidden Orders in Stock Markets
We empirically study the market impact of trading orders. We are specically interested in large
trading orders that are executed incrementally, which we call hidden orders. These are reconstructed
based on information about market member codes using data from the Spanish Stock Market and the
London Stock Exchange. We nd that market impact is strongly concave, approximately increasing
as the square root of order size. Furthermore, as a given order is executed, the impact grows in time
according to a power-law; after the order is nished, it reverts to a level of about 0:5We empirically study the market impact of trading orders. We are specically interested in large
trading orders that are executed incrementally, which we call hidden orders. These are reconstructed
based on information about market member codes using data from the Spanish Stock Market and the
London Stock Exchange. We nd that market impact is strongly concave, approximately increasing
as the square root of order size. Furthermore, as a given order is executed, the impact grows in time
according to a power-law; after the order is nished, it reverts to a level of about 0:5Refereed Working Papers / of international relevanc
Surface-Barrier Effects in the Microwave Second-Harmonic Response of Superconductors in the Mixed State
We report on transient effects in the microwave second-order response of
different type of superconductors in the mixed state. The samples have
contemporarily been exposed to a dc magnetic field, varying with a constant
rate of 60 Oe/s, and a pulsed microwave magnetic field. The time evolution of
the signal radiated at the second-harmonic frequency of the driving field has
been measured for about 500 s from the instant in which the dc-field sweep has
been stopped, with sampling time of about 0.3 s. We show that the
second-harmonic signal exhibits two relaxation regimes; an initial exponential
decay, which endures roughly 10 s, and a logarithmic decay in the time scale of
minutes. Evidence is given that the decay in the time scale of minutes is ruled
by magnetic relaxation over the surface barrier.Comment: 6 pages, 6 embedded figure
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