905 research outputs found
Comments on T-dualities of Ramond-Ramond Potentials
The type IIA/IIB effective actions compactified on T^d are known to be
invariant under the T-duality group SO(d, d; Z) although the invariance of the
R-R sector is not so direct to see. Inspired by a work of Brace, Morariu and
Zumino,we introduce new potentials which are mixture of R-R potentials and the
NS-NS 2-form in order to make the invariant structure of R-R sector more
transparent. We give a simple proof that if these new potentials transform as a
Majorana-Weyl spinor of SO(d, d; Z), the effective actions are indeed invariant
under the T-duality group. The argument is made in such a way that it can apply
to Kaluza-Klein forms of arbitrary degree. We also demonstrate that these new
fields simplify all the expressions including the Chern-Simons term.Comment: 26 pages; LaTeX; major version up; discussion on the Chern-Simons
term added; references adde
Weyl Groups in AdS(3)/CFT(2)
The system of D1 and D5 branes with a Kaluza-Klein momentum is
re-investigated using the five-dimensional U-duality group E_{6(+6)}(Z). We
show that the residual U-duality symmetry that keeps this D1-D5-KK system
intact is generically given by a lift of the Weyl group of F_{4(+4)}, embedded
as a finite subgroup in E_{6(+6)}(Z). We also show that the residual U-duality
group is enhanced to F_{4(+4)}(Z) when all the three charges coincide. We then
apply the analysis to the AdS(3)/CFT(2) correspondence, and discuss that among
28 marginal operators of CFT(2) which couple to massless scalars of AdS(3)
gravity at boundary, 16 would behave as exactly marginal operators for generic
D1-D5-KK systems. This is shown by analyzing possible three-point couplings
among 42 Kaluza-Klein scalars with the use of their transformation properties
under the residual U-duality group.Comment: 20 pages, 3 figue
Highly complex mitochondrial DNA genealogy in an endemic Japanese subterranean breeding brown frog Rana tagoi (Amphibia, Anura, Ranidae).
The endemic Japanese frog Rana tagoi is unique among Holarctic brown frogs in that it breeds in small subterranean streams. Using mitochondrial 16S ribosomal RNA and NADH dehydrogenase subunit 1 genes, we investigated genealogical relationships among geographic samples of this species together with its relative R. sakuraii, which is also a unique stream breeder. These two species together form a monophyletic group, within which both are reciprocally paraphyletic. Rana tagoi is divided into two major clades (Clade A and B) that are composed of 14 genetic groups. Rana sakuraii is included in Clade A and split into two genetic groups, one of which forms a clade (Subclade A-2) with sympatric R. tagoi. This species-level paraphyly appears to be caused by incomplete taxonomy, in addition to introgressive hybridization and/or incomplete lineage sorting. Rana tagoi strongly differs from other Japanese anurans in its geographic pattern of genetic differentiation, most probably in relation to its unique reproductive habits. Taxonomically, R. tagoi surely includes many cryptic species
High-field magnetization and magnetic phase transition in CeOs2Al10
We have studied the magnetization of CeOs2Al10 in high magnetic fields up to
55 T for H // a and constructed the magnetic phase diagram for H // a. The
magnetization curve shows a concave H dependence below T_max \sim40 K which is
higher than the transition temperature T_0 \sim29 K. The magnetic
susceptibility along the a-axis shows a smooth and continuous decrease down to
\sim20 K below T_max \sim40 K without showing an anomaly at T_0. From these two
results, a Kondo singlet is formed below T_max and coexists with the antiferro
magnetic order below T_0. We also propose that the larger suppression of the
spin degrees of freedom along the a-axis than along the c-axis below T_max is
associated with the origin of the antiferro magnetic component.Comment: 4 pages, 4 figures, to appear in Phys. Rev. B, Rapid Commu
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