2,277 research outputs found
On the energy-momentum tensor
We clarify the relation among canonical, metric and Belinfante's
energy-momentum tensors for general tensor field theories. For any tensor field
T, we define a new tensor field \til {\bm T}, in terms of which the
Belinfante tensor is readily computed. We show that the latter is the one that
arises naturally from Noether Theorem for an arbitrary spacetime and it
coincides on-shell with the metric one.Comment: 11 pages, 1 figur
Motion and Trajectories of Particles Around Three-Dimensional Black Holes
The motion of relativistic particles around three dimensional black holes
following the Hamilton-Jacobi formalism is studied. It follows that the
Hamilton-Jacobi equation can be separated and reduced to quadratures in analogy
with the four dimensional case. It is shown that: a) particles are trapped by
the black hole independently of their energy and angular momentum, b) matter
alway falls to the centre of the black hole and cannot understake a motion with
stables orbits as in four dimensions. For the extreme values of the angular
momentum of the black hole, we were able to find exact solutions of the
equations of motion and trajectories of a test particle.Comment: Plain TeX, 9pp, IPNO-TH 93/06, DFTUZ 93/0
U(1) Noncommutative Gauge Fields and Magnetogenesis
The connection between the Lorentz invariance violation in the lagrangean
context and the quantum theory of noncommutative fields is established for the
U(1) gauge field. The modified Maxwell equations coincide with other
derivations obtained using different procedures. These modified equations are
interpreted as describing macroscopic ones in a polarized and magnetized
medium. A tiny magnetic field (seed) emerges as particular static solution that
gradually increases once the modified Maxwell equations are solved as a
self-consistent equations system.Comment: 4 page
SU(2) Kinetic Mixing Terms and Spontaneous Symmetry Breaking
The non-abelian generalization of the Holdom model --{\it i.e.} a theory with
two gauge fields coupled to the kinetic mixing term -- is considered. Contrarily to the abelian case, the group
structure is explicitly broken to . For SU(2) this fact implies
that the residual gauge symmetry as well as the Lorentz symmetry is
spontaneusly broken. We show that this mechanism provides of masses for the
involved particles. Also, the model presents instanton solutions with a
redefined coupling constant.Comment: 9pp. typos and clarifications are adde
Analysis of gene expression in the Leishmania life cycle : Leishmania (Viannia) braziliensis and Leishmania (Viannia) peruviana model
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