scholarly journals A TORSIONAL TOPOLOGICAL INVARIANT

2007 ◽  
Vol 22 (29) ◽  
pp. 5237-5244 ◽  
Author(s):  
H. T. NIEH
Keyword(s):  
Affine Connection ◽  
Euler Class ◽  
Christoffel Symbol ◽  
Space Time ◽  
Topological Invariant ◽  
Point Of View ◽  
Underlying Space ◽  
Recent Developments ◽  
Theory Point ◽  
Curvature And Torsion

Curvature and torsion are the two tensors characterizing a general Riemannian space–time. In Einstein's general theory of gravitation, with torsion postulated to vanish and the affine connection identified to the Christoffel symbol, only the curvature tensor plays the central role. For such a purely metric geometry, two well-known topological invariants, namely the Euler class and the Pontryagin class, are useful in characterizing the topological properties of the space–time. From a gauge theory point of view, and especially in the presence of spin, torsion naturally comes into play, and the underlying space–time is no longer purely metric. We describe a torsional topological invariant, discovered in 1982, that has now found increasing usefulness in recent developments.

scholarly journals Perturbative Gravity and Gauge Theory Relations: A Review

2012 ◽  
Vol 2012 ◽  
pp. 1-29 ◽  
Author(s):  
Thomas Søndergaard
Keyword(s):  
Field Theory ◽  
Gauge Theory ◽  
String Theory ◽  
Gauge Theories ◽  
Point Of View ◽  
Tree Level ◽  
General Properties ◽  
Recent Developments ◽  
Theory Point

This paper is dedicated to the amazing Kawai-Lewellen-Tye relations, connecting perturbative gravity and gauge theories at tree level. The main focus is onn-point derivations and general properties both from a string theory and pure field theory point of view. In particular, the field theory part is based on some very recent developments.

scholarly journals Static vacuum solutions on curved space–times with torsion

2018 ◽  
Vol 33 (16) ◽  
pp. 1850095 ◽  
Author(s):  
Hamid Shabani ◽  
Amir Hadi Ziaie
Keyword(s):  
Affine Connection ◽  
Space Time ◽  
Field Equations ◽  
Static Vacuum ◽  
Naked Singularities ◽  
Intrinsic Angular Momentum ◽  
Curvature And Torsion ◽  
Scalar Invariants ◽  
Vacuum Solutions ◽  
Matter Energy

The Einstein–Cartan–Kibble–Sciama ( ECKS ) theory of gravity naturally extends Einstein’s general relativity ( GR ) to include intrinsic angular momentum (spin) of matter. The main feature of this theory consists of an algebraic relation between space–time torsion and spin of matter, which indeed deprives the torsion of its dynamical content. The Lagrangian of ECKS gravity is proportional to the Ricci curvature scalar constructed out of a general affine connection so that owing to the influence of matter energy–momentum and spin, curvature and torsion are produced and interact only through the space–time metric. In the absence of spin, the space–time torsion vanishes and the theory reduces to GR . It is however possible to have torsion propagation in vacuum by resorting to a model endowed with a nonminimal coupling between curvature and torsion. In the present work we try to investigate possible effects of the higher order terms that can be constructed from space–time curvature and torsion, as the two basic constituents of Riemann–Cartan geometry. We consider Lagrangians that include fourth-order scalar invariants from curvature and torsion and then investigate the resulting field equations. The solutions that we find show that there could exist, even in vacuum, nontrivial static space–times that admit both black holes and naked singularities.

Chemical analysis: Information contribution of results

1991 ◽  
Vol 56 (3) ◽  
pp. 505-559 ◽  
Author(s):  
Karel Eckschlager
Keyword(s):  
Analytical Chemistry ◽  
Information Theory ◽  
Set Theory ◽  
Fuzzy Set Theory ◽  
Information Gain ◽  
Analytical Signal ◽  
Point Of View ◽  
System A ◽  
Review Analysis ◽  
Theory Point

In this review, analysis is treated as a process of gaining information on chemical composition, taking place in a stochastic system. A model of this system is outlined, and a survey of measures and methods of information theory is presented to an extent as useful for qualitative or identification, quantitative and trace analysis and multicomponent analysis. It is differentiated between information content of an analytical signal and information gain, or amount of information, obtained by the analysis, and their interrelation is demonstrated. Some notions of analytical chemistry are quantified from the information theory and system theory point of view; it is also demonstrated that the use of fuzzy set theory can be suitable. The review sums up the principal results of the series of 25 papers which have been published in this journal since 1971.

scholarly journals GRIBOV PROBLEM FOR GAUGE THEORIES: A PEDAGOGICAL INTRODUCTION

2004 ◽  
Vol 01 (04) ◽  
pp. 423-441 ◽  
Author(s):  
GIAMPIERO ESPOSITO ◽  
DIEGO N. PELLICCIA ◽  
FRANCESCO ZACCARIA
Keyword(s):  
Cross Sections ◽  
Gauge Theories ◽  
Functional Integral ◽  
Point Of View ◽  
Spherically Symmetric ◽  
Abelian Gauge ◽  
Gauge Transformations ◽  
Recent Developments ◽  
Gribov Ambiguity ◽  
Gribov Copies

The functional-integral quantization of non-Abelian gauge theories is affected by the Gribov problem at non-perturbative level: the requirement of preserving the supplementary conditions under gauge transformations leads to a nonlinear differential equation, and the various solutions of such a nonlinear equation represent different gauge configurations known as Gribov copies. Their occurrence (lack of global cross-sections from the point of view of differential geometry) is called Gribov ambiguity, and is here presented within the framework of a global approach to quantum field theory. We first give a simple (standard) example for the SU(2) group and spherically symmetric potentials, then we discuss this phenomenon in general relativity, and recent developments, including lattice calculations.

DESITTER GAUGE THEORY OF GRAVITATION

2003 ◽  
Vol 14 (01) ◽  
pp. 41-48 ◽  
Author(s):  
G. ZET ◽  
V. MANTA ◽  
S. BABETI
Keyword(s):  
Gauge Theory ◽  
Riemann Tensor ◽  
Space Time ◽  
Point Of View ◽  
Field Equations ◽  
Minkowski Space Time ◽  
Strength Tensor ◽  
Group A ◽  
Theory Of Gravitation ◽  
Tensor Formula

A deSitter gauge theory of gravitation over a spherical symmetric Minkowski space–time is developed. The "passive" point of view is adapted, i.e., the space–time coordinates are not affected by group transformations; only the fields change under the action of the symmetry group. A particular ansatz for the gauge fields is chosen and the components of the strength tensor are computed. An analytical solution of Schwarzschild–deSitter type is obtained in the case of null torsion. It is concluded that the deSitter group can be considered as a "passive" gauge symmetry for gravitation. Because of their complexity, all the calculations, inclusive of the integration of the field equations, are performed using an analytical program conceived in GRTensorII for MapleV. The program allows one to compute (without using a metric) the strength tensor [Formula: see text], Riemann tensor [Formula: see text], Ricci tensor [Formula: see text], curvature scalar [Formula: see text], field equations, and the integration of these equations.

scholarly journals Nature itself in a mirror space–time

2015 ◽  
Vol 93 (10) ◽  
pp. 1005-1008 ◽  
Author(s):  
Rasulkhozha S. Sharafiddinov
Keyword(s):  
Dirac Equation ◽  
Minkowski Space ◽  
Space Time ◽  
Point Of View ◽  
Classical Solutions ◽  
Left Handed ◽  
Minkowski Space Time ◽  
Energy And Momentum ◽  
The Right ◽  
Structure Of Matter

The unity of the structure of matter fields with flavor symmetry laws involves that the left-handed neutrino in the field of emission can be converted into a right-handed one and vice versa. These transitions together with classical solutions of the Dirac equation testify in favor of the unidenticality of masses, energies, and momenta of neutrinos of the different components. If we recognize such a difference in masses, energies, and momenta, accepting its ideas about that the left-handed neutrino and the right-handed antineutrino refer to long-lived leptons, and the right-handed neutrino and the left-handed antineutrino are short-lived fermions, we would follow the mathematical logic of the Dirac equation in the presence of the flavor symmetrical mass, energy, and momentum matrices. From their point of view, nature itself separates Minkowski space into left and right spaces concerning a certain middle dynamical line. Thereby, it characterizes any Dirac particle both by left and by right space–time coordinates. It is not excluded therefore that whatever the main purposes each of earlier experiments about sterile neutrinos, namely, about right-handed short-lived neutrinos may serve as the source of facts confirming the existence of a mirror Minkowski space–time.

Low-energy Ion Beam Biotechnology at Chiang Mai University

2009 ◽  
Vol 1181 ◽  
Author(s):  
Liangdeng Yu ◽  
S. Anuntalabhochai
Keyword(s):  
Gene Transfer ◽  
Biological Effects ◽  
Ion Beam ◽  
Point Of View ◽  
Low Energy ◽  
Theoretical Point ◽  
Chiang Mai ◽  
Naked Dna ◽  
Recent Developments ◽  
Cell Envelopes

AbstractMeV-ion beam has long been applied to biology research and applications for many decades as highly energetic ions are undoubtedly able to interact directly with biology molecules to cause changes in biology. However, low-energy ion beam at tens of keV and even lower has also been found to have significant biological effects on living materials. The finding has led to applications of ion-beam induced mutation and gene transfer. From the theoretical point of view, the low-energy ion beam effects on biology are difficult to understand since the ion range is so short that the ions can hardly directly interact with the key biological molecules for the changes. This talk introduces interesting aspects of low-energy ion beam biology, including basis of ion beam biotechnology and recent developments achieved in Chiang Mai University in relevant applications such as mutation and gene transfer and investigations on mechanisms involved in the low-energy ion interaction with biological matter such as eV-keV ion beam bombardments of naked DNA and the cell envelopes.

scholarly journals Electron-capture modes with realistic nuclear structure calculations

2019 ◽  
Vol 21 ◽  
pp. 4
Author(s):  
P. G. Giannaka ◽  
T. S. Kosmas
Keyword(s):  
Electron Capture ◽  
Cross Sections ◽  
Nuclear Reactions ◽  
Random Phase ◽  
Point Of View ◽  
Electron Neutrino ◽  
Β Decay ◽  
Decay Modes ◽  
Theory Point ◽  
Nuclear Structure Calculations

Nuclear electron capture posses prominent position among other weak interaction processes occuring in explosive nucleosynthesis. In particular, this process plays important role in the core-colapse of massive stars by modifying the electron to baryon ratio Ye. From a nuclear theory point of view, such processes may be studied by using the same nuclear methods (e.g. the quasi-particle random phase approximation, QRPA), employed in the present work with these used for the one-body charge changing nuclear reactions (β-decay modes, charged-current electron-neutrino absorption by nuclei, etc). In this work we calculate e−-capture cross sections on 56Fe using two different approaches. At first, original cross section calculations are perfored by using the pn-QRPA method considering all the accessible transitions of the final nucleus 56Mn. Secondly, we evaluate the Gamow-Teller strength distributions and obtain the cross sections at the limit of zero-momentum transfer. The agreement between the two methods is very good.

scholarly journals Optimal control of affine connection control systems from the point of view of Lie algebroids

2014 ◽  
Vol 11 (09) ◽  
pp. 1450038 ◽  
Author(s):  
Lígia Abrunheiro ◽  
Margarida Camarinha
Keyword(s):  
Optimal Control ◽  
Vector Field ◽  
Control Systems ◽  
Lie Groups ◽  
Optimal Control Problems ◽  
Affine Connection ◽  
Point Of View ◽  
Lie Algebroids ◽  
Control Problems ◽  
Hamiltonian Vector Field

The purpose of this paper is to use the framework of Lie algebroids to study optimal control problems (OCPs) for affine connection control systems (ACCSs) on Lie groups. In this context, the equations for critical trajectories of the problem are geometrically characterized as a Hamiltonian vector field.

The main trends in the Russian tourism and hospitality market from the point of view of Russian travel agencies

2018 ◽  
Vol 10 (4) ◽  
pp. 412-420 ◽  
Author(s):  
Aleksandr Gudkov ◽  
Elena Dedkova ◽  
Kristina Dudina
Keyword(s):  
Relevant Information ◽  
Tourism Industry ◽  
Point Of View ◽  
Content Type ◽  
Qualitative Research Methodology ◽  
Recent Developments ◽  
Survey Results ◽  
The Subject ◽  
Tourism And Hospitality ◽  
The Impact

PurposeThis paper aims to discuss recent developments in the Russian tourism industry and the main reasons for new initiatives in local destination development.Design/methodology/approachThe study is based on qualitative research methodology. A summary of key literature is presented alongside the analysis of the survey results.FindingsThis paper sheds light on the challenges and changes that took place in the Russian tourism business between 2014 and 2017. The subject is poorly covered in academic literature. The basic data for analysis presented in official statistics are scarce. Therefore a more effective way of obtaining relevant information was to conduct a survey using a semi-structured questionnaire, with tourism business actors as respondents.Research limitations/implicationsThis paper provides mostly conceptual analysis based on limited empirical data; directions for further empirical research are proposed in the conclusion.Originality/valueThe paper reveals something of the impact of economic and geopolitical factors, both negative and positive ones, on the restructuring of the Russian tourism market and the emergence of promising opportunities for the development of new domestic destinations. As a result, tourism market actors are able to become more diverse.

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