1,596 research outputs found
The Standard Model and its Generalizations in Epstein-Glaser Approach to Renormalization Theory II: the Fermion Sector and the Axial Anomaly
We complete our study of non-Abelian gauge theories in the framework of
Epstein-Glaser approach to renormalization theory including in the model an
arbitrary number of Dirac Fermions. We consider the consistency of the model up
to the third order of the perturbation theory. In the second order we obtain
pure group theoretical relations expressing a representation property of the
numerical coefficients appearing in the left and right handed components of the
interaction Lagrangian. In the third order of the perturbation theory we obtain
the the condition of cancellation of the axial anomaly.Comment: 38 pages, LATEX 2e, extensive rewritting, some errors eliminate
The Interaction of Quantum Gravity with Matter
The interaction of (linearized) gravitation with matter is studied in the
causal approach up to the second order of perturbation theory. We consider the
generic case and prove that gravitation is universal in the sense that the
existence of the interaction with gravitation does not put new constraints on
the Lagrangian for lower spin fields. We use the formalism of quantum off-shell
fields which makes our computation more straightforward and simpler.Comment: 25 page
Self-Phase-Matched Second-Harmonic and White-Light Generation in a Biaxial Zinc Tungstate Single Crystal
Second-order nonlinear optical materials are used to generate new frequencies by exploiting second-harmonic generation (SHG), a phenomenon where a nonlinear material generates light at double the optical frequency of the input beam. Maximum SHG is achieved when the pump and the generated waves are in phase, for example through birefringence in uniaxial crystals. However, applying these materials usually requires a complicated cutting procedure to yield a crystal with a particular orientation. Here we demonstrate the first example of phase matching under the normal incidence of SHG in a biaxial monoclinic single crystal of zinc tungstate. The crystal was grown by the micro-pulling-down method with the (102) plane perpendicular to the growth direction. Additionally, at the same time white light was generated as a result of stimulated Raman scattering and multiphoton luminescence induced by higher-order effects such as three-photon luminescence enhanced by cascaded third-harmonic generation. The annealed crystal offers SHG intensities approximately four times larger than the as grown one; optimized growth and annealing conditions may lead to much higher SHG intensities
g-engineering in hybrid rotaxanes to create AB and AB2 electron spin systems: EPR spectroscopic studies of weak interactions between dissimilar electron spin qubits
Hybrid [2]rotaxanes and pseudorotaxanes are reported where the magnetic interaction between dissimilar spins is controlled to create AB and AB2 electron spin systems,allowing independent control of weakly interacting S =1=2 centers
Quantum Gravitational Bremsstrahlung, Massless versus Massive Gravity
The massive spin-2 quantum gauge theory previously developed is applied to
calculate gravitational bremsstrahlung. It is shown that this theory is unique
and free from defects. In particular, there is no strong coupling if the
graviton mass becomes small. The cross sections go over smoothly into the ones
of the massless theory in the limit of vanishing graviton mass. The massless
cross sections are calculated for the full tensor theory.Comment: 13 pages, 1 figur
The 4th International Conference on Social Responsibility, Ethics, and Sustainable Business. Athens, Greece, October 8 & 9, 2015
Properties of the Scalar Universal Equations
The variational properties of the scalar so--called ``Universal'' equations
are reviewed and generalised. In particular, we note that contrary to earlier
claims, each member of the Euler hierarchy may have an explicit field
dependence. The Euler hierarchy itself is given a new interpretation in terms
of the formal complex of variational calculus, and is shown to be related to
the algebra of distinguished symmetries of the first source form.Comment: 15 pages, LaTeX articl
Regularization in quantum field theory from the causal point of view
The causal approach to perturbative quantum field theory is presented in
detail, which goes back to a seminal work by Henri Epstein and Vladimir Jurko
Glaser in 1973. Causal perturbation theory is a mathematically rigorous
approach to renormalization theory, which makes it possible to put the
theoretical setup of perturbative quantum field theory on a sound mathematical
basis. Epstein and Glaser solved this problem for a special class of
distributions, the time-ordered products, that fulfill a causality condition,
which itself is a basic requirement in axiomatic quantum field theory. In their
original work, Epstein and Glaser studied only theories involving scalar
particles. In this review, the extension of the method to theories with higher
spin, including gravity, is presented. Furthermore, specific examples are
presented in order to highlight the technical differences between the causal
method and other regularization methods, like, e.g. dimensional regularization.Comment: 75 pages, 8 figures, style file included, some comments and
references adde
Local Nature of Coset Models
The local algebras of the maximal Coset model C_max associated with a chiral
conformal subtheory A\subset B are shown to coincide with the local relative
commutants of A in B, provided A contains a stress energy tensor.
Making the same assumption, the adjoint action of the unique
inner-implementing representation U^A associated with A\subset B on the local
observables in B is found to define net-endomorphisms of B. This property is
exploited for constructing from B a conformally covariant holographic image in
1+1 dimensions which proves useful as a geometric picture for the joint
inclusion A\vee C_max \subset B.
Immediate applications to the analysis of current subalgebras are given and
the relation to normal canonical tensor product subfactors is clarified. A
natural converse of Borchers' theorem on half-sided translations is made
accessible.Comment: 33 pages, no figures; typos, minor improvement
The genus Inula and their metabolites : From ethnopharmacological to medicinal uses
ETHNOPHARMACOLOGICAL RELEVANCE: The genus Inula comprises more than one hundred species widespread in temperate regions of Europe and Asia. Uses of this genus as herbal medicines have been first recorded by the Greek and Roman ancient physicians. In the Chinese Pharmacopoeia, from the 20 Inula spp. distributed in China, three are used as Traditional Chinese medicines, named Tumuxiang, Xuanfuhua and Jinfeicao. These medicines are used as expectorants, antitussives, diaphoretics, antiemetics, and bactericides. Moreover, Inula helenium L. which is mentioned in Minoan, Mycenaean, Egyptian/Assyrian pharmacotherapy and Chilandar Medical Codex, is good to treat neoplasm, wound, freckles and dandruff. Many other Inula spp. are used in Ayurvedic and Tibetan traditional medicinal systems for the treatment of diseases such as bronchitis, diabetes, fever, hypertension and several types of inflammation. This review is a critical evaluation of the published data on the more relevant ethnopharmacological and medicinal uses of Inula spp. and on their metabolites biological activities. This study allows the identification of the ethnopharmacological knowledge of this genus and will provide insight into the emerging pharmacological applications of Inula spp. facilitating the prioritirization of future investigations. The corroboration of the ethnopharmacological applications described in the literature with proved biological activities of Inula spp. secondary metabolites will also be explored.University of Aveiro, Fundação para a Ciência e a Tecnologia (FCT, Portugal), the European Union, QREN, FEDER, COMPETE, for funding the Organic Chemistry Research Unit (QOPNA) (project PEst-/QUI/UI0062/2013; FCOMP-01-0124-FEDER-037296). The work was also supported by a grant of UEFISCDI, Romania, PN-II-PT-PCCA-2 no. 134/2012.info:eu-repo/semantics/publishedVersio
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