69 research outputs found
No interactions for a collection of Weyl gravitons intermediated by a scalar field
The cross-couplings among several Weyl gravitons (described in the free limit
by a sum of linearized Weyl actions) in the presence of a scalar field are
studied with the help of the deformation theory based on local BRST cohomology.
Under the hypotheses of locality, smoothness of the interactions in the
coupling constant, Poincare invariance, (background) Lorentz invariance, and
the preservation of the number of derivatives on each field, together with the
supplementary assumption that the internal metric defined by the sum of Weyl
lagrangians is positively defined, we prove that there are no consistent
cross-interactions among different Weyl gravitons in the presence of a scalar
field. The couplings of a single Weyl graviton to a scalar field are also
discussed.Comment: 53 page
Lagrangian interactions within a special class of covariant mixed-symmetry type tensor gauge fields
Consistent nontrivial interactions within a special class of covariant
mixed-symmetry type tensor gauge fields of degree three are constructed from
the deformation of the solution to the master equation combined with specific
cohomological techniques. In spacetime dimensions strictly greater than four,
the only consistent interaction terms are those gauge invariant under the
original symmetry. Only in four spacetime dimensions the gauge symmetry is
found deformed.Comment: 24 pages; two equations corrected; matches the published versio
Imaging of atomic orbitals with the Atomic Force Microscope - experiments and simulations
Atomic force microscopy (AFM) is a mechanical profiling technique that allows
to image surfaces with atomic resolution. Recent progress in reducing the noise
of this technique has led to a resolution level where previously undetectable
symmetries of the images of single atoms are observed. These symmetries are
related to the nature of the interatomic forces. The Si(111)-(7x7) surface is
studied by AFM with various tips and AFM images are simulated with chemical and
electrostatic model forces. The calculation of images from the tip-sample
forces is explained in detail and the implications of the imaging parameters
are discussed. Because the structure of the Si(111)-(7x7) surface is known very
well, the shape of the adatom images is used to determine the tip structure.
The observability of atomic orbitals by AFM and scanning tunneling microscopy
is discussed.Comment: 21 pages, 17 figure
On the uniqueness of D=11 interactions among a graviton, a massless gravitino and a three-form. III: Graviton and gravitini
Under the hypotheses of smoothness of the interactions in the coupling
constant, locality, Poincare invariance, Lorentz covariance, and the
preservation of the number of derivatives on each field in the Lagrangian of
the interacting theory (the same number of derivatives like in the free
Lagrangian), we prove that in D=11 there are no cross-interactions between the
graviton and the massless gravitino and also no self-interactions in the
Rarita-Schwinger sector. A comparison with the case D=4 is briefly discussed.Comment: 16 page
Four-dimensional couplings among BF and matter theories from BRST cohomology
The local and manifestly covariant Lagrangian interactions in four spacetime
dimensions that can be added to a ``free'' model that describes a generic
matter theory and an abelian BF theory are constructed by means of deforming
the solution to the master equation on behalf of specific cohomological
techniques.Comment: 45 pages, no figure
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