2,301 research outputs found
Harmonic space and quaternionic manifolds
We find a principle of harmonic analyticity underlying the quaternionic
(quaternion-K\"ahler) geometry and solve the differential constraints which
define this geometry. To this end the original -dimensional quaternionic
manifold is extended to a bi-harmonic space. The latter includes additional
harmonic coordinates associated with both the tangent local group and
an extra rigid group rotating the complex structures. Then the
constraints can be rewritten as integrability conditions for the existence of
an analytic subspace in the bi-harmonic space and solved in terms of two
unconstrained potentials on the analytic subspace. Geometrically, the
potentials have the meaning of vielbeins associated with the harmonic
coordinates. We also establish a one-to-one correspondence between the
quaternionic spaces and off-shell supersymmetric sigma-models coupled to
supergravity. The general sigma-model Lagrangian when written in
the harmonic superspace is composed of the quaternionic potentials. Coordinates
of the analytic subspace are identified with superfields describing
matter hypermultiplets and a compensating hypermultiplet of supergravity.
As an illustration we present the potentials for the symmetric quaternionic
spaces.Comment: 44 pages, LATEX, JHU-TIPAC-920023, ENSLAPP-L-405-92, MPI-Ph/92-8
Four Dimensional Integrable Theories
There exist many four dimensional integrable theories. They include self-dual
gauge and gravity theories, all their extended supersymmetric generalisations,
as well the full (non-self-dual) N=3 super Yang-Mills equations. We review the
harmonic space formulation of the twistor transform for these theories which
yields a method of producing explicit connections and metrics. This formulation
uses the concept of harmonic space analyticity which is closely related to that
of quaternionic analyticity. (Talk by V. Ogievetsky at the G\"ursey Memorial
Conference I, Istanbul, June 1994)Comment: 11 pages, late
On the growth of von Neumann dimension of harmonic spaces of semipositive line bundles over covering manifolds
We study the harmonic space of line bundle valued forms over a covering
manifold with a discrete group action , and obtain an asymptotic
estimate for the -dimension of the harmonic space with respect to the
tensor times in the holomorphic line bundle and the type
of the differential form, when is semipositive. In particular, we
estimate the -dimension of the corresponding reduced -Dolbeault
cohomology group. Essentially, we obtain a local estimate of the pointwise norm
of harmonic forms with valued in semipositive line bundles over Hermitian
manifolds
Protein signatures using electrostatic molecular surfaces in harmonic space
We developed a novel method based on the Fourier analysis of protein
molecular surfaces to speed up the analysis of the vast structural data
generated in the post-genomic era. This method computes the power spectrum of
surfaces of the molecular electrostatic potential, whose three-dimensional
coordinates have been either experimentally or theoretically determined. Thus
we achieve a reduction of the initial three-dimensional information on the
molecular surface to the one-dimensional information on pairs of points at a
fixed scale apart. Consequently, the similarity search in our method is
computationally less demanding and significantly faster than shape comparison
methods. As proof of principle, we applied our method to a training set of
viral proteins that are involved in major diseases such as Hepatitis C, Dengue
fever, Yellow fever, Bovine viral diarrhea and West Nile fever. The training
set contains proteins of four different protein families, as well as a
mammalian representative enzyme. We found that the power spectrum successfully
assigns a unique signature to each protein included in our training set, thus
providing a direct probe of functional similarity among proteins. The results
agree with established biological data from conventional structural
biochemistry analyses.Comment: 9 pages, 10 figures Published in PeerJ (2013),
https://peerj.com/articles/185
Local symmetry of harmonic spaces as determined by the spectra of small geodesic spheres
We show that in any harmonic space, the eigenvalue spectra of the Laplace
operator on small geodesic spheres around a given point determine the norm
of the covariant derivative of the Riemannian curvature tensor in
that point. In particular, the spectra of small geodesic spheres in a harmonic
space determine whether the space is locally symmetric. For the proof we use
the first few heat invariants and consider certain coefficients in the radial
power series expansions of the curvature invariants and of
the geodesic spheres. Moreover, we obtain analogous results for geodesic balls
with either Dirichlet or Neumann boundary conditions.Comment: 18 pages, LaTeX. Added a few lines in the introduction, corrected a
few typos. Final version. Accepted for publication in GAF
CMB Lensing Reconstruction in Real Space
We explore the reconstruction of the gravitational lensing field of the
cosmic microwave background in real space showing that very little statistical
information is lost when estimators of short range on the celestial sphere are
used in place of the customary estimators in harmonic space, which are nonlocal
and in principle require a simultaneous analysis of the entire sky without any
cuts or excisions. Because virtually all the information relevant to lensing
reconstruction lies on angular scales close to the resolution scale of the sky
map, the gravitational lensing dilatation and shear fields (which unlike the
deflection field or lensing potential are directly related to the observations
in a local manner) may be reconstructed by means of quadratic combinations
involving only very closely separated pixels. Even though harmonic space
provides a more natural context for understanding lensing reconstruction
theoretically, the real space methods developed here have the virtue of being
faster to implement and are likely to prove useful for analyzing realistic maps
containing a galactic cut and possibly numerous small excisions to exclude
point sources that cannot be reliably subtracted.Comment: 21 pages, 8 figure
- …