158 research outputs found
On Spin(7) holonomy metric based on SU(3)/U(1)
We investigate the holonomy metric of cohomogeneity one with the
principal orbit . A choice of U(1) in the two dimensional Cartan
subalgebra is left as free and this allows manifest (= the
Weyl group) symmetric formulation. We find asymptotically locally conical (ALC)
metrics as octonionic gravitational instantons. These ALC metrics have orbifold
singularities in general, but a particular choice of the U(1) subgroup gives a
new regular metric of holonomy. Complex projective space that is a supersymmetric four-cycle appears as a singular orbit. A
perturbative analysis of the solution near the singular orbit shows an evidence
of a more general family of ALC solutions. The global topology of the manifold
depends on a choice of the U(1) subgroup. We also obtain an -normalisable
harmonic 4-form in the background of the ALC metric.Comment: 21 pages, Latex, Introduction slightly expanded, an error in section
6 corrected and references added, (v3) minor correction
Octonionic Yang-Mills Instanton on Quaternionic Line Bundle of Spin(7) Holonomy
The total space of the spinor bundle on the four dimensional sphere S^4 is a
quaternionic line bundle that admits a metric of Spin(7) holonomy. We consider
octonionic Yang-Mills instanton on this eight dimensional gravitational
instanton. This is a higher dimensional generalization of (anti-)self-dual
instanton on the Eguchi-Hanson space.
We propose an ansatz for Spin(7) Yang-Mills field and derive a system of
non-linear ordinary differential equations. The solutions are classified
according to the asymptotic behavior at infinity. We give a complete solution,
when the gauge group is reduced to a product of SU(2) subalgebras in Spin(7).
The existence of more general Spin(7) valued solutions can be seen by making an
asymptotic expansion.Comment: A reference added; 22 pages,a final version to appear J.Geom.Phy
Characteristics of nonlinear terahertz-wave radiation generated by mid-infrared femtosecond pulse laser excitation
We report on efficient terahertz-wave generation in organic and inorganic crystals by nonlinear wavelength conversion approach using a 3.3 ÎŒm femtosecond pulse laser. Experimental results reveal the relation between pump power and terahertz-wave output power, which is proportional to the square of the pump power at the range of mega- to tera-watt cmâ2 class even if the pump wavelength is different. Damage threshold of organic and inorganic crystals are recorded 0.6 and 18 tera-watt cmâ2 by reducing several undesirable nonlinear optical effects using mid-infrared source
Harmonic Forms and Deformation of ALC metrics with Spin(7) holonomy
Asymptotically locally conical (ALC) metric of exceptional holonomy has an
asymptotic circle bundle structure that accommodates the M theory circle in
type IIA reduction. Taking Spin(7) metrics of cohomogeneity one as explicit
examples, we investigate deformations of ALC metrics, in particular that change
the asymptotic S^1 radius related to the type IIA string coupling constant.
When the canonical four form of Spin(7) holonomy is taken to be anti-self-dual,
the deformations of Spin(7) metric are related to the harmonic self-dual four
forms, which are given by solutions to a system of first order differential
equations, due to the metric ansatz of cohomogeneity one. We identify the
L^2-normalizable solution that deforms the asymptotic radius of the M theory
circle.Comment: 33 pages, no figure, minor corrections, reference adde
Umbilical Cord Blood as an Alternative Source of Reduced-Intensity Hematopoietic Stem Cell Transplantation for Chronic Epstein-Barr VirusâAssociated T or Natural Killer Cell Lymphoproliferative Diseases
AbstractChronic Epstein-Barr virusâassociated T/natural killer cell lymphoproliferative diseases represented by chronic active Epstein-Barr virus infection are lethal but are curable with several courses of chemotherapy and allogeneic hematopoietic stem cell transplantation (HSCT). Recently, we reported that reduced-intensity conditioning (RIC) provided better outcomes than myeloablative conditioning because RIC was less toxic. However, it was unclear whether cord blood transplantation (CBT) works in the context of RIC. We retrospectively analyzed 17 patients who underwent RIC followed by bone marrow transplantation (RIC-BMT) and 15 patients who underwent RIC followed by CBT (RIC-CBT). The representative regimen was fludarabine and melphalan based. The overall survival rates with RIC-BMT and RIC-CBT were 92.9% ± 6.9% and 93.3% ± 6.4%, respectively (P = .87). One patient died of lung graft-versus-host disease after RIC-BMT, and 1 patient died of multiple viral infections after RIC-CBT. Although cytotoxic chemotherapy was also immunosuppressive and might contribute to better donor cell engraftment after RIC-HSCT, the rate of engraftment failure after RIC-CBT was still higher than that after RIC-BMT (not significant); however, patients who had experienced graft failure were successfully rescued with a second HSCT. Unrelated cord blood can be an alternative source for RIC-HSCT if a patient has no family donor
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