527 research outputs found

### The Projective Unitary Irreducible Representations of the Galilei Group in 1+2 Dimensions

We give an elementary analysis of the multiplicator group of the Galilei
group in 1+2 dimensions $G^{\uparrow}_{+}$. For a non-trivial multiplicator we
give a list of all the corresponding projective unitary irreducible
representations of $G^{\uparrow}_{+}$.Comment: 15 pages, LATEX, preprint IFA-FT-391-1993, Decembe

### Conformal Invariance in Classical Field Theory

A geometric generalization of first-order Lagrangian formalism is used to
analyse a conformal field theory for an arbitrary primary field. We require
that global conformal transformations are Noetherian symmetries and we prove
that the action functional can be taken strictly invariant with respect to
these transformations. In other words, there does not exists a "Chern-Simons"
type Lagrangian for a conformally invariant Lagrangian theory.Comment: 18 pages, PLAIN-TE

### Massive gravity from descent equations

Both massless and massive gravity are derived from descent equations
(Wess-Zumino consistency conditions). The massive theory is a continuous
deformation of the massless one.Comment: 8 pages, no figur

### 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

### Perturbative Gravity in the Causal Approach

Quantum theory of the gravitation in the causal approach is studied up to the
second order of perturbation theory. We prove gauge invariance and
renormalizability in the second order of perturbation theory for the pure
gravity system (massless and massive). Then we investigate the interaction of
massless gravity with matter (described by scalars and spinors) and massless
Yang-Mills fields. We obtain a difference with respect to the classical field
theory due to the fact that in quantum field theory one cannot enforce the
divergenceless property on the vector potential and this spoils the
divergenceless property of the usual energy-momentum tensor. To correct this
one needs a supplementary ghost term in the interaction Lagrangian.Comment: 50 pages, no figures, some changes in the last sectio

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