6,071 research outputs found
A Pedagogical Intrinsic Approach to Relative Entropies as Potential Functions of Quantum Metrics: the - Family
The so-called -z-\textit{R\'enyi Relative Entropies} provide a huge
two-parameter family of relative entropies which includes almost all well-known
examples of quantum relative entropies for suitable values of the parameters.
In this paper we consider a log-regularized version of this family and use it
as a family of potential functions to generate covariant symmetric
tensors on the space of invertible quantum states in finite dimensions. The
geometric formalism developed here allows us to obtain the explicit expressions
of such tensor fields in terms of a basis of globally defined differential
forms on a suitable unfolding space without the need to introduce a specific
set of coordinates. To make the reader acquainted with the intrinsic formalism
introduced, we first perform the computation for the qubit case, and then, we
extend the computation of the metric-like tensors to a generic -level
system. By suitably varying the parameters and , we are able to recover
well-known examples of quantum metric tensors that, in our treatment, appear
written in terms of globally defined geometrical objects that do not depend on
the coordinates system used. In particular, we obtain a coordinate-free
expression for the von Neumann-Umegaki metric, for the Bures metric and for the
Wigner-Yanase metric in the arbitrary -level case.Comment: 50 pages, 1 figur
Dynamical aspects in the Quantizer-Dequantizer formalism
The use of the quantizer-dequantizer formalism to describe the evolution of a
quantum system is reconsidered. We show that it is possible to embed a manifold
in the space of quantum states of a given auxiliary system by means of an
appropriate quantizer-dequantizer system. If this manifold of states is
invariant with respect to some unitary evolution, the quantizer-dequantizer
system provides a classical-like realization of such dynamics, which in general
is non linear. Integrability properties are also discussed. Weyl systems and
generalized coherente states are used as a simple illustration of these ideas.Comment: 15 page
Schwinger's Picture of Quantum Mechanics IV: Composition and independence
The groupoids description of Schwinger's picture of quantum mechanics is
continued by discussing the closely related notions of composition of systems,
subsystems, and their independence. Physical subsystems have a neat algebraic
description as subgroupoids of the Schwinger's groupoid of the system. The
groupoids picture offers two natural notions of composition of systems: Direct
and free products of groupoids, that will be analyzed in depth as well as their
universal character. Finally, the notion of independence of subsystems will be
reviewed, finding that the usual notion of independence, as well as the notion
of free independence, find a natural realm in the groupoids formalism. The
ideas described in this paper will be illustrated by using the EPRB experiment.
It will be observed that, in addition to the notion of the non-separability
provided by the entangled state of the system, there is an intrinsic
`non-separability' associated to the impossibility of identifying the entangled
particles as subsystems of the total system.Comment: 32 pages. Comments are welcome
Covariant Jacobi Brackets for Test Particles
We show that the space of observables of test particles carries a natural
Jacobi structure which is manifestly invariant under the action of the
Poincar\'{e} group. Poisson algebras may be obtained by imposing further
requirements. A generalization of Peierls procedure is used to extend this
Jacobi bracket on the space of time-like geodesics on Minkowski space-time.Comment: 13 pages Submitted to MPL
Geometry from divergence functions and complex structures
Motivated by the geometrical structures of quantum mechanics, we introduce an
almost-complex structure on the product of any parallelizable
statistical manifold . Then, we use to extract a pre-symplectic form and
a metric-like tensor on from a divergence function. These tensors
may be pulled back to , and we compute them in the case of an N-dimensional
symplex with respect to the Kullback-Leibler relative entropy, and in the case
of (a suitable unfolding space of) the manifold of faithful density operators
with respect to the von Neumann-Umegaki relative entropy.Comment: 19 pages, comments are welcome
Covariant Variational Evolution and Jacobi Brackets: Fields
The analysis of the covariant brackets on the space of functions on the
solutions to a variational problem in the framework of contact geometry
initiated in the companion letter Ref.19 is extended to the case of the
multisymplectic formulation of the free Klein-Gordon theory and of the free
Schr\"{o}dinger equation.Comment: 16 page
First assessment of age and sex structures of elephants by using dung size analysis in a West African savannah
1. An age and sex structure study of the West African savannah elephant (Loxodonta africana africana) population of the Nazinga Game ranch (Burkina Faso) was carried out using direct sightings of individuals near water points, where they group during hot periods of the day, and droppings circumference measurements of dung pile along line transects, during the dry seasons of 2007 and 2008. The age structure, from direct observation data, was estimated by classifying the individuals into 9 age-class-categories based on body size and eruption (length) of tusks.2. The frequency distribution of number of individuals into the age-class-categories showed high similarity with the distribution of circumference measurements of dung-piles that the individuals were seen depositing. Fifty dung-piles measured soon after they were deposited (Class A) and after they dried (to class C) showed a significant difference between the circumference measurements in relation to the time elapsed between the measurements.3. The frequency distribution of dung circumference classes of the observed elephants was similar to that of the dung-piles measured along the transects in 2008. Therefore, dung-piles measurements were used to estimate the Nazinga Game Ranch savanna elephant population’s age and sex structures at the end of dry seasons of 2007 and 2008. We advocated that the Nazinga elephant population consisted mainly of sub-adults.4. The sex ratio was estimated to be in favour of females (1/2). The age-class-specific sex ratio was uneven for calves and young individuals, while being in favour of females with adults. Individuals of less than 1 year represented 6% of the population during the study period
Humor Styles as New Resources in a Primary Preventive Perspective: Reducing Resistance to Change for Negotiation
CT-based tumour response criteria compared after combined treatment for liver metastases of colorectal cancer
open6noPurpose: The aim of this analysis is to compare different tumour response
criteria (TRC) after chemotherapy combined with bevacizumab in liver
metastases from colorectal cancer (mCRC) to ascertain the best early
prognostic indicator of response.
Methods and Materials: 103 target liver metastases from 65 mCRC patients
treated with chemoterapy plus bevacizumab were examined at the Istituto
Oncologico Veneto IOV-IRCSS (March 2008-January 2013). All patients had
baseline CT and at least one follow-up scan. Tumour response was
retrospectively analyzed by two radiologists using RECIST1.1, modified Choi,
and Chun morphologic criteria. Tumour response, classified as good (complete
or partial response) or poor (stable or progressive disease), was compared
with progression-free survival (PFS) at first follow-up (t1) and time of best
response. Interobserver agreement and concordance between TRC were
measured.
Results: At t1, 32.31% showed a good response according to RECIST1.1
(median PFS 11.1), 84.62% according to Choi (median PFS 10.8). These
percentages rose to 49.23% (median PFS 12.1) and 87.69% (median PFS
10.8), respectively, at the time of best response. According to Chun, 67.69%
showed a good response at the time of best response (median PFS 10.8). The
Choi criteria detected a higher proportion of good responders at t1, showing a
better correlation with PFS; all methods correlated with PFS at the time of best
response.
Conclusion: The Choi criteria proved more consistent in the early detection of
response in mCRC treated with chemotherapy plus bevacizumab,
underscoring the importance of using these criteria in the early assessment of
response to combined treatment.openopenVarotto, A.; Di Grazia, L.; Aliberti, C.; Bergamo, F.; Nardin, M.; Pomerri, F.Varotto, A.; Di Grazia, L.; Aliberti, C.; Bergamo, F.; Nardin, M.; Pomerri, Fabi
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