599 research outputs found
Quartic double solids with ordinary singularities
We study the mixed Hodge structure on the third homology group of a threefold
which is the double cover of projective three-space ramified over a quartic
surface with a double conic. We deal with the Torelli problem for such
threefolds.Comment: 14 pages, presented at the Conference Arnol'd 7
Neutrino masses, cosmological bound and four zero Yukawa textures
Four zero neutrino Yukawa textures in a specified weak basis, combined with
symmetry and type-I seesaw, yield a highly constrained and predictive
scheme. Two alternately viable light neutrino Majorana mass matrices
result with inverted/normal mass ordering. Neutrino
masses, Majorana in character and predicted within definite ranges with
laboratory and cosmological inputs, will have their sum probed cosmologically.
The rate for decay, though generally below the reach of
planned experiments, could approach it in some parameter region. Departure from
symmetry due to RG evolution from a high scale and consequent CP
violation, with a Jarlskog invariant whose magnitude could almost reach
, are explored.Comment: Published versio
Homological Type of Geometric Transitions
The present paper gives an account and quantifies the change in topology
induced by small and type II geometric transitions, by introducing the notion
of the \emph{homological type} of a geometric transition. The obtained results
agree with, and go further than, most results and estimates, given to date by
several authors, both in mathematical and physical literature.Comment: 36 pages. Minor changes: A reference and a related comment in Remark
3.2 were added. This is the final version accepted for publication in the
journal Geometriae Dedicat
DNA Sexing of the Philippine Eagle (Pithecophaga jefferyi Ogilvie-Grant) in Captivity at the Philippine Eagle Center, Davao City, Philippines
The Philippine eagle is a sexually monomorphic raptor which lacks the sex-linked morphology determining the gender especially in the juveniles. Thus, a PCR amplification technique was used to determine the sex of 24 eagles at different stages of development (2 to 37 years old) in captivity at the Philippine Eagle Center, Malagos Davao City. Fractions of the sex-linked genes, CHD-W and CHD-Z of each individual were amplified. Ka Brianne (female) and Jag (male) having 9 offspring conceived through artificial insemination were used as positive controls for sex identification of 22 other individuals. Two individuals of Gallus domesticus with confirmed genders were also included and run through PCR amplification together with the Philippine eagles using primers CHDFORNEW and CHDREVNEW to test the method. Females revealed two distinct bands (290 bp and 280 bp in size) while the males revealed only a single band of 280 bp. Eleven eagles were found to be females while 13 were found to be males. DNA sexing gave a 100% confirmation of the assigned sexes of the eagles, which were obtained through morphometric analysis done by personnel at the captive breeding center. DNA sexing could be a practical technique in sexing newly hatched eaglet and juveniles, naming of eagles, establishing life history characteristics, and pairing attempt or assignment of partners in the threatened avian species such as the Philippine eagles
Knot homology via derived categories of coherent sheaves II, sl(m) case
Using derived categories of equivariant coherent sheaves we construct a knot
homology theory which categorifies the quantum sl(m) knot polynomial. Our knot
homology naturally satisfies the categorified MOY relations and is
conjecturally isomorphic to Khovanov-Rozansky homology. Our construction is
motivated by the geometric Satake correspondence and is related to Manolescu's
by homological mirror symmetry.Comment: 51 pages, 9 figure
Constraining the Kahler Moduli in the Heterotic Standard Model
Phenomenological implications of the volume of the Calabi-Yau threefolds on
the hidden and observable M-theory boundaries, together with slope stability of
their corresponding vector bundles, constrain the set of Kaehler moduli which
give rise to realistic compactifications of the strongly coupled heterotic
string. When vector bundles are constructed using extensions, we provide simple
rules to determine lower and upper bounds to the region of the Kaehler moduli
space where such compactifications can exist. We show how small these regions
can be, working out in full detail the case of the recently proposed Heterotic
Standard Model. More explicitely, we exhibit Kaehler classes in these regions
for which the visible vector bundle is stable. On the other hand, there is no
polarization for which the hidden bundle is stable.Comment: 28 pages, harvmac. Exposition improved, references and one figure
added, minor correction
Relativistic theory of magnetic scattering of x rays: Application to ferromagnetic iron
We present a detailed description of a first-principles formalism for magnetic scattering of circularly polar- ized x rays from solids in the framework of the fully relativistic spin-polarized multiple-scattering theory. The scattering amplitudes are calculated using a standard time-dependent perturbation theory to second order in the electron-photon interaction vertex. Particular attention is paid to understanding the relative importance of the positive- and negative-energy solutions of the Dirac equation to the scattering amplitude. The advantage of the present theory as compared with other recent works on magnetic x-ray scattering is that, being fully relativistic, spin-orbit coupling and spin-polarization effects are treated on an equal footing. Second, the electron Green’s function expressed in terms of the path operators in the multiple-scattering theory allows us to include the contribution of the crystalline environment to the scattering amplitude. To illustrate the use of the method we have done calculations on the anomalous magnetic scattering at the K , L_II , and L_III absorption edges of ferromagnetic iron
Holomorphic symplectic geometry: a problem list
A list of open problems on holomorphic symplectic, contact and Poisson
manifolds
Resonant X-Ray Magnetic Scattering from CoO
We analyze the recent experiment [W. Neubeck {\em et al.}, Phys. Rev. B
\vol(60,1999,R9912)] for the resonant x-ray magnetic scattering (RXMS) around
the K edge of Co in the antiferromagnet CoO. We propose a mechanism of the RXMS
to make the states couple to the magnetic order: the intraatomic exchange
interaction between the and the states and the - mixing to the
states of neighboring Co atoms. These couplings induce the orbital moment
in the states and make the scattering tensor antisymmetric. Using a
cluster model, we demonstrate that this modification gives rise to a large RXMS
intensity in the dipole process, in good agreement with the experiment. We also
find that the pre-edge peak is generated by the transition to the states
in the quadrupole process, with negligible contribution of the dipole process.
We also discuss the azimuthal angle dependence of the intensity.Comment: 15 pages, 8 figure
Satellite holmium M-edge spectra from the magnetic phase via resonant x-ray scattering
Developing an expression of resonant x-ray scattering (RXS) amplitude which
is convenient for investigating the contributions from the higher rank tensor
on the basis of a localized electron picture, we analyze the RXS spectra from
the magnetic phases of Ho near the absorption edges. At the
edge in the uniform helical phase, the calculated spectra of the absorption
coefficient, the RXS intensities at the first and second satellite spots
capture the properties the experimental data possess, such as the spectral
shapes and the peak positions. This demonstrates the plausibility of the
adoption of the localized picture in this material and the effectiveness of the
spectral shape analysis. The latter point is markedly valuable since the
azimuthal angle dependence, which is one of the most useful informations RXS
can provides, is lacking in the experimental conditions. Then, by focusing on
the temperature dependence of the spectral shape at the second satellite spot,
we expect that the spectrum is the contribution of the pure rank two profile in
the uniform helical and the conical phases while that is dominated by the rank
one profile in the intermediate temperature phase, so-called spin slip phase.
The change of the spectral shape as a function of temperature indicates a
direct evidence of the change of magnetic structures undergoing. Furthermore,
we predict that the intensity, which is the same order observed at the second
satellite spot, is expected at the fourth satellite spot from the conical phase
in the electric dipolar transition.Comment: 24 pages, 5 figure
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