280 research outputs found
On the q-deformation of the NJL model
Using a q-deformed fermionic algebra we perform explicitly a deformation of
the Nambu-Jona-Lasinio (NJL) Hamiltonian. In the Bogoliubov-Valatin approach we
obtain the deformed version of the functional for the total energy, which is
minimized to obtain the corresponding gap equation. The breaking of chiral
symmetry and its restoration in the limit are then discussed.Comment: 5 eps figure
The Wigner function associated to the Rogers-Szego polynomials
We show here that besides the well known Hermite polynomials, the q-deformed
harmonic oscillator algebra admits another function space associated to a
particular family of q-polynomials, namely the Rogers-Szego polynomials. Their
main properties are presented, the associated Wigner function is calculated and
its properties are discussed. It is shown that the angle probability density
obtained from the Wigner function is a well-behaved function defined in the
interval [-Pi,Pi), while the action probability only assumes integer values
greater or equal than zero. It is emphasized the fact that the width of the
angle probability density is governed by the free parameter q characterizing
the polynomial.Comment: 12 pages, 2 (mathemathica) figure
Schwinger, Pegg and Barnett approaches and a relationship between angular and Cartesian quantum descriptions II: Phase Spaces
Following the discussion -- in state space language -- presented in a
preceding paper, we work on the passage from the phase space description of a
degree of freedom described by a finite number of states (without classical
counterpart) to one described by an infinite (and continuously labeled) number
of states. With that it is possible to relate an original Schwinger idea to the
Pegg and Barnett approach to the phase problem. In phase space language, this
discussion shows that one can obtain the Weyl-Wigner formalism, for both
Cartesian {\em and} angular coordinates, as limiting elements of the discrete
phase space formalism.Comment: Subm. to J. Phys A: Math and Gen. 7 pages, sequel of quant-ph/0108031
(which is to appear on J.Phys A: Math and Gen
Finite-dimensional Schwinger basis, deformed symmetries, Wigner function, and an algebraic approach to quantum phase
Schwinger's finite (D) dimensional periodic Hilbert space representations are
studied on the toroidal lattice {\ee Z}_{D} \times {\ee Z}_{D} with specific
emphasis on the deformed oscillator subalgebras and the generalized
representations of the Wigner function. These subalgebras are shown to be
admissible endowed with the non-negative norm of Hilbert space vectors. Hence,
they provide the desired canonical basis for the algebraic formulation of the
quantum phase problem. Certain equivalence classes in the space of labels are
identified within each subalgebra, and connections with area-preserving
canonical transformations are examined. The generalized representations of the
Wigner function are examined in the finite-dimensional cyclic Schwinger basis.
These representations are shown to conform to all fundamental conditions of the
generalized phase space Wigner distribution. As a specific application of the
Schwinger basis, the number-phase unitary operator pair in {\ee Z}_{D} \times
{\ee Z}_{D} is studied and, based on the admissibility of the underlying
q-oscillator subalgebra, an {\it algebraic} approach to the unitary quantum
phase operator is established. This being the focus of this work, connections
with the Susskind-Glogower- Carruthers-Nieto phase operator formalism as well
as standard action-angle Wigner function formalisms are examined in the
infinite-period limit. The concept of continuously shifted Fock basis is
introduced to facilitate the Fock space representations of the Wigner function.Comment: 19 pages, no figure
Generalized squeezing operators, bipartite Wigner functions and entanglement via Wehrl's entropy functionals
We introduce a new class of unitary transformations based on the su(1,1) Lie
algebra that generalizes, for certain particular representations of its
generators, well-known squeezing transformations in quantum optics. To
illustrate our results, we focus on the two-mode bosonic representation and
show how the parametric amplifier model can be modified in order to generate
such a generalized squeezing operator. Furthermore, we obtain a general
expression for the bipartite Wigner function which allows us to identify two
distinct sources of entanglement, here labelled by dynamical and kinematical
entanglement. We also establish a quantitative estimate of entanglement for
bipartite systems through some basic definitions of entropy functionals in
continuous phase-space representations.Comment: 16 page
Quantum information distributors: Quantum network for symmetric and asymmetric cloning in arbitrary dimension and continuous limit
We show that for any Hilbert-space dimension, the optimal universal quantum
cloner can be constructed from essentially the same quantum circuit, i.e., we
find a universal design for universal cloners. In the case of infinite
dimensions (which includes continuous variable quantum systems) the universal
cloner reduces to an essentially classical device. More generally, we construct
a universal quantum circuit for distributing qudits in any dimension which acts
covariantly under generalized displacements and momentum kicks. The behavior of
this covariant distributor is controlled by its initial state. We show that
suitable choices for this initial state yield both universal cloners and
optimized cloners for limited alphabets of states whose states are related by
generalized phase-space displacements.Comment: 10 revtex pages, no figure
Pemetrexed enhances membrane PD-L1 expression and potentiates T cell-mediated cytotoxicity by anti-PD-L1 antibody therapy in non-small-cell lung cancer
Immunotherapy has significantly changed the treatment landscape for advanced non-small-cell lung cancer (NSCLC) with the introduction of drugs targeting programmed cell death protein-1 (PD-1) and programmed cell death ligand-1 (PD-L1). In particular, the addition of the anti-PD-1 antibody pembrolizumab to platinum-pemetrexed chemotherapy resulted in a significantly improved overall survival in patients with non-squamous NSCLC, regardless of PD-L1 expression. In this preclinical study, we investigated whether chemotherapy can modulate PD-L1 expression in non-squamous NSCLC cell lines, thus potentially affecting immunotherapy efficacy. Among different chemotherapeutic agents tested, only pemetrexed increased PD-L1 levels by activating both mTOR/P70S6K and STAT3 pathways. Moreover, it also induced the secretion of cytokines, such as IFN-Îł and IL-2, by activated peripheral blood mononuclear cells PBMCs that further stimulated the expression of PD-L1 on tumor cells, as demonstrated in a co-culture system. The anti-PD-1/PD-L1 therapy enhanced T cell-mediated cytotoxicity of NSCLC cells treated with pemetrexed and expressing high levels of PD-L1 in comparison with untreated cells. These data may explain the positive results obtained with pemetrexed-based chemotherapy combined with pembrolizumab in PD-L1-negative NSCLC and can support pemetrexed as one of the preferable chemotherapy partners for immunochemotherapy combination regimens
Quantum Tunneling in Nuclear Fusion
Recent theoretical advances in the study of heavy ion fusion reactions below
the Coulomb barrier are reviewed. Particular emphasis is given to new ways of
analyzing data, such as studying barrier distributions; new approaches to
channel coupling, such as the path integral and Green function formalisms; and
alternative methods to describe nuclear structure effects, such as those using
the Interacting Boson Model. The roles of nucleon transfer, asymmetry effects,
higher-order couplings, and shape-phase transitions are elucidated. The current
status of the fusion of unstable nuclei and very massive systems are briefly
discussed.Comment: To appear in the January 1998 issue of Reviews of Modern Physics. 13
Figures (postscript file for Figure 6 is not available; a hard copy can be
requested from the authors). Full text and figures are also available at
http://nucth.physics.wisc.edu/preprints
Mixed connective tissue disease: state of the art on clinical practice guidelines
Mixed connective tissue disease (MCTD) is a complex overlap disease with features of different autoimmune connective tissue diseases (CTDs) namely systemic sclerosis, poly/dermatomyositis and systemic lupus erythematous in patients with antibodies targeting the U1 small nuclear ribonucleoprotein particle. In this narrative review, we summarise the results of a systematic literature research which was performed as part of the European Reference Network on Rare and Complex Connective Tissue and Musculoskeletal Diseases project, aimed at evaluating existing clinical practice guidelines (CPGs) or recommendations. Since no specific CPGs on MCTD were found, other CPGs developed for other CTDs were taken into consideration in order to discuss what can be applied to MCTD even if designed for other diseases. Three major objectives were proposed for the future development of CPGs: MCTD diagnosis (diagnostic criteria), MCTD initial and follow-up evaluations, MCTD treatment. Early diagnosis, epidemiological data, assessment of burden of disease and QOL aspects are among the unmet needs identified by patient
Heisenberg-type structures of one-dimensional quantum Hamiltonians
We construct a Heisenberg-like algebra for the one dimensional infinite
square-well potential in quantum mechanics. The ladder operators are realized
in terms of physical operators of the system as in the harmonic oscillator
algebra. These physical operators are obtained with the help of variables used
in a recently developed non commutative differential calculus. This
\textquotedblleft square-well algebra\textquotedblright is an example of an
algebra in a large class of generalized Heisenberg algebras recently
constructed. This class of algebras also contains -oscillators as a
particular case. We also discuss the physical content of this large class of
algebras.Comment: 11 pages. The title and abstract were modified and minor corrections
were made in the paper's core. Final version to appear in Phys. Rev.
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