Search results for "Introduction"
showing 10 items of 104 documents
The radiation class: a set of temporal gauges
1993
We present in a path integral framework a class of gauges for QED that are both temporal and yet do not display the notorious singularity of the naive temporal gauge. These gauges follow from a generalised radiation gauge, where the Coulomb gauge fixingsis “smeared out”. We show that the use of two gauge fixings necessitates the incorporation of gauge dependent Coulomb interactions. The correctness of our theory is demonstrated in two ways: we can reduce to the true degrees of freedom and we show that it reproduces some gaugeinvariant results of perturbation theory. Although Landshoff's α prescription for the temporal gauge can be understood as a limit of our class, extra terms also appear.…
GENERALIZED GAUGE TRANSFORMATIONS AND HIDDEN SYMMETRY IN THE STANDARD MODEL
1992
A recently proposed, new construction of the Standard Model based on the graded Lie algebra SU (2|1) is analyzed in some depth. The essential ingredient is an algebraic superconnection which incorporates both the gauge fields and the Higgs fields and whose curvature automatically leads to a spontaneously broken realization of the theory. The mechanism of hiding the original algebraic structure is unorthodox and is due to the specific, "noncommutative" realization of SU (2|1). The model is characterized by a constant background supercurvature which is invariant under arbitrary, constant SU (2|1) gauge transformations. This background field whose effect is analogous to the action of a consta…
Cosmological perturbations in extended electromagnetism. General gauge invariant approach
2013
A certain vector-tensor (VT) theory is revisited. It was proposed and analyzed as a theory of electromagnetism without the standard gauge invariance. Our attention is first focused on a detailed variational formulation of the theory, which leads to both a modified Lorentz force and the true energy momentum tensor of the vector field. The theory is then applied to cosmology. A complete gauge invariant treatment of the scalar perturbations is presented. For appropriate gauge invariant variables describing the scalar modes of the vector field (A-modes), it is proved that the evolution equations of these modes do not involve the scalar modes appearing in General Relativity (GR-modes), which are…
Non-abelian gauge dynamics of slowly moving fermions
1987
We study the dynamics generated by local gauge invariance under a non-abelianSU(N) group for two nonrelativistic particles interacting through the effect of the group charges. We describe the local gauge invariant potential which contains the exchange of infinitely many gluons. We discuss the possible implications of our result.
GAUGE-HIGGS UNIFICATION MODELS WITH COSET SPACE DIMENSIONAL REDUCTION SCHEME
2009
We investigate the gauge-Higgs unification models within the scheme of the coset space dimensional reduction, beginning with two types of set up; fourteen-dimensional gauge theory with simple gauge groups and ten-dimensional gauge theory with direct product gauge groups. We found some phenomenologically acceptable models through an exhaustive search for the candidates of the coset spaces, the gauge group in higher dimension, and fermion representation.
Running soft parameters in SUSY models with multiple U(1) gauge factors
2012
Abstract We generalize the two-loop renormalization group equations for the parameters of the softly broken SUSY gauge theories given in the literature to the most general case when the gauge group contains more than a single Abelian gauge factor. The complete method is illustrated at two-loop within a specific example and compared to some of the previously proposed partial treatments.
Newtonian and relativistic emission coordinates
2009
Emission coordinates are those generated by positioning systems. Positioning systems are physical systems constituted by four emitters broadcasting their respective times by means of sound or light signals. We analyze the incidence of the space-time causal structure on the construction of emission coordinates. The Newtonian case of four emitters at rest is analyzed and contrasted with the corresponding situation in special relativity.
Note di Abū Naṣr al-Fārābī sulla verità e falsità dell’astrologia
2020
Il presente contributo propone l’introduzione, la traduzione italiana e il commento delle Note sulla verità e falsità dell’astrologia (Nukat fī mā yaṣiḥḥu wa-mā lā yaṣiḥḥu min aḥkām al-nuǧūm) di Abū Naṣr al-Fārābī (m. 950). Tale scritto non è stato trasmesso direttamente dal suo autore né ci è giunto nella sua redazione definitiva, bensì in forma di appunti ricopiati da un grammatico di nome Abū Isḥāq al-Baġdādī. In trenta brevi capitoli al-Fārābī spiega ciò che è accessibile e ciò che è inaccessibile alle predizioni astrologiche e quali aspetti di tale scienza sia opportuno accogliere o respingere.
lNTRODUZlONE
2023
Brief introduction to the volume "Viaggiare nell’immaginario. Immaginare il viaggio" edited by Giulia de Spuches and Leonardo Mercatanti.
The Characteristics of initial public offering for innovative small and medium-sized firms: the case of young french bio/medtech firms
2017
The various government measures in favor of innovative SMEs, the number of biotechnology firms listed on the stock exchange over the last ten years, the characteristics of their pre-introduction financing are different factors that justify a particular interest for these firms and their methods of introduction (discount, float, quotation procedure). Different tests of mean difference have significant results. Comparing with a control sample, we found that SME in this sector are listed on the stock exchange faster, by making greater use of the open-price offer procedure (OPO) and are subject to greater prior financing by financial stockholders. Although the ownership of the capital and the d…