1,920 research outputs found

### Nodes, Monopoles and Confinement in 2+1-Dimensional Gauge Theories

In the presence of Chern-Simons interactions the wave functionals of physical
states in 2+1-dimensional gauge theories vanish at anumber of nodal points. We
show that those nodes are located at some classical configurations which carry
a non-trivial magnetic charge. In abelian gauge theories this fact explains why
magnetic monopoles are suppressed by Chern-Simons interactions. In non-abelian
theories it suggests a relevant role for nodal gauge field configurations in
the confinement mechanism of Yang-Mills theories. We show that the vacuum nodes
correspond to the chiral gauge orbits of reducible gauge fields with
non-trivial magnetic monopole components.Comment: 11 pages, revtex, no figures

### Symplectic gauge fields and dark matter

The dynamics of symplectic gauge fields provides a consistent framework for
fundamental interactions based on spin three gauge fields. One remarkable
property is that symplectic gauge fields only have minimal couplings with
gravitational fields and not with any other field of the Standard Model.
Interactions with ordinary matter and radiation can only arise from radiative
corrections. In spite of the gauge nature of symplectic fields they acquire a
mass by the Coleman-Weinberg mechanism which generates Higgs-like mass terms
where the gravitational field is playing the role of a Higgs field. Massive
symplectic gauge fields weakly interacting with ordinary matter are natural
candidates for the dark matter component of the Universe.Comment: 16 page

### Universalty and Ultraviolet Regularizations of Chern-Simons Theory

The universality of radiative corrections to the gauge coupling constant $k$
of Chern-Simons theory is studied in a very general regularization scheme. We
show that the effective coupling constant $k$ induced by radiative corrections
depends crucially on the balance between the ultraviolet behavior of scalar and
pseudoscalar terms in the regularized action. There are three different
regimes. When the ultraviolet leading term is scalar the coupling $k$ is
shifted to $k+h^{\vee}$.However, if the leading term is pseudoscalar the shift
is $k+s h^{\vee}$ with $s=0$ or $s=2$ depending on the sign of such a term. In
the borderline case when the scalar and pseudoscalar terms have the same
ultraviolet behavior the shift of $k$ becomes arbitrary (even non-integer) and
depends on the parameters of the regularization. We also show that the
coefficient of the induced gravitational Chern-Simons term is different for the
three regimes and has the same universality properties than the effective
coupling constant $k$. The results open the possibility of a connection with
non-rational two-dimensional conformal theories in the borderline regime.Comment: 34 pages, harvmac, no changes, 6 Postscript figures (now included

### Vacuum Boundary Effects

The effect of boundary conditions on the vacuum structure of quantum field
theories is analysed from a quantum information viewpoint. In particular, we
analyse the role of boundary conditions on boundary entropy and entanglement
entropy. The analysis of boundary effects on massless free field theories
points out the relevance of boundary conditions as a new rich source of
information about the vacuum structure. In all cases the entropy does not
increase along the flow from the ultraviolet to the infrared.Comment: 10 page

### Maximal Non-Abelian Gauges and Topology of Gauge Orbit Space

We introduce two maximal non-abelian gauge fixing conditions on the space of
gauge orbits M for gauge theories over spaces with dimensions d < 3. The gauge
fixings are complete in the sense that describe an open dense set M_0 of the
space of gauge orbits M and select one and only one gauge field per gauge orbit
in M_0. There are not Gribov copies or ambiguities in these gauges. M_0 is a
contractible manifold with trivial topology. The set of gauge orbits which are
not described by the gauge conditions M \ M_0 is the boundary of M_0 and
encodes all non-trivial topological properties of the space of gauge orbits.
The gauge fields configurations of this boundary M \ M_0 can be explicitly
identified with non-abelian monopoles and they are shown to play a very
relevant role in the non-perturbative behaviour of gauge theories in one, two
and three space dimensions. It is conjectured that their role is also crucial
for quark confinement in 3+1 dimensional gauge theories.Comment: 31 pages, harvmac, 1 figur

### The critical transition of Coulomb impurities in gapped graphene

The effect of supercritical charge impurities in graphene is very similar to
the supercritical atomic collapses in QED for Z > 137, but with a much lower
critical charge. In this sense graphene can be considered as a natural testing
ground for the analysis of quantum field theory vacuum instabilities. We
analyze the quantum transition from subcritical to supercritical charge regimes
in gapped graphene in a common framework that preserves unitarity for any value
of charge impurities. In the supercritical regime it is possible to introduce
boundary conditions which control the singular behavior at the impurity. We
show that for subcritical charges there are also non-trivial boundary
conditions which are similar to those that appear in QED for nuclei in the
intermediate regime 118<Z<137. We analyze the behavior of the energy levels
associated to the different boundary conditions. In particular, we point out
the existence of new bound states in the subcritical regime which include a
negative energy bound state in the attractive Coulomb regime. A remarkable
property is the continuity of the energy spectral flow under variation of the
impurity charge even when jumping across the critical charge transition. We
also remark that the energy levels of Hydrogenoid bound states at critical
values of charge impurities act as focal points of the spectral flow.Comment: 24 pages, 7 figure

### Astroparticle Physics at Eastern Colombia

We present the emerging panorama of Astroparticle Physics at Eastern
Colombia, and describe several ongoing projects, most of them related to the
Latin American Giant Observatory (LAGO) Project. This research work is carried
out at the Grupo de Investigaciones en Relatividad y Gravitaci\'on of
Universidad Industrial de Santander.Comment: 19 pages, 8 figure

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