13,287 research outputs found
Topological gravity localization on a delta-function like Brane
Besides the String Theory context, the quantum General Relativity can be
studied by the use of constrained topological field theories. In the celebrated
Plebanski formalism, the constraints connecting topological field theories and
gravity are imposed in space-times with trivial topology. In the braneworld
context there are two distinct regions of the space-time, namely, the bulk and
the braneworld volume. In this work we show how to construct topological
gravity in a scenario containing one extra dimension and a delta-function like
3-brane which naturally emerges from a spontaneously broken discrete symmetry.
Starting from a D=5 theory we obtain the action for General Relativity in the
Palatini form in the bulk as well as in the braneworld volume. This result is
important for future insights about quantum gravity in brane scenarios.Comment: 4 page
Theoretical investigation of moir\'e patterns in quantum images
Moir\'e patterns are produced when two periodic structures with different
spatial frequencies are superposed. The transmission of the resulting structure
gives rise to spatial beatings which are called moir\'e fringes. In classical
optics, the interest in moir\'e fringes comes from the fact that the spatial
beating given by the frequency difference gives information about details(high
spatial frequency) of a given spatial structure. We show that moir\'e fringes
can also arise in the spatial distribution of the coincidence count rate of
twin photons from the parametric down-conversion, when spatial structures with
different frequencies are placed in the path of each one of the twin beams. In
other words,we demonstrate how moir\'e fringes can arise from quantum images
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