Penrose transform
In theoretical physics, the Penrose transform, introduced by Roger Penrose (1967, 1968, 1969), is a complex analogue of the Radon transform that relates massless fields on spacetime, or more precisely the space of solutions to massless field equations, to sheaf cohomology groups on complex projective space. The projective space in question is the twistor space, a geometrical space naturally associated to the original spacetime, and the twistor transform is also geometrically natural in the sense of integral geometry. The Penrose transform is a major component of classical twistor theory.
Overview
Abstractly, the Penrose transform operates on a double fibration of a space Y, over two spaces X and Z
In the classical Penrose transform, Y is the
where G is a complex semisimple Lie group and H1 and H2 are parabolic subgroups.
The Penrose transform operates in two stages. First, one
Example
The classical example is given as follows
- The "twistor space" Z is complex projective 3-space CP3, which is also the Grassmannian Gr1(C4) of lines in 4-dimensional complex space.
- X = Gr2(C4), the Grassmannian of 2-planes in 4-dimensional complex space. This is a compactification of complex Minkowski space.
- Y is the flag manifoldwhose elements correspond to a line in a plane of C4.
- G is the group SL4(C) and H1 and H2 are the parabolic subgroups fixing a line or a plane containing this line.
The maps from Y to X and Z are the natural projections.
Using spinor index notation, the Penrose transform gives a bijection between solutions to the spin massless field equation
Penrose–Ward transform
The Penrose–Ward transform is a nonlinear modification of the Penrose transform, introduced by
See also
References
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- Eastwood, M.G. (2001) [1994], "Penrose transform", Encyclopedia of Mathematics, EMS Press
- David, Liana (2001), The Penrose transform and its applications (PDF), University of Edinburgh; Doctor of Philosophy thesis.
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