11,201 research outputs found
in generalized supergravity
We showed in previous work that for homogeneous Yang-Baxter (YB) deformations
of AdSS, the open string metric and coupling, and as a result the
closed string density , remain undeformed. In this work,
in addition to extending these results to the deformation associated with the
modified CYBE, or -deformation, we identify the Page forms as the open
string counterpart for RR fields and demonstrate case by case that the non-zero
Page forms remain invariant under YB deformations. We give a physical meaning
to the Killing vector of generalized supergravity and show for all YB
deformations: 1) appears as a current for center of mass motion on the
worldvolume of a D-branes probing the background, 2) is equal to the
divergence of the noncommutativity parameter, 3) exhibits "holographic"
behavior, where the radial component of vanishes at the AdS boundary, and
4) in pure spinor formalism is related to a certain state in the BRST
cohomology.Comment: 11 pages, 2 column; v2 references updated; v3 to appear in EPJ
Electron-positron annihilation into phi f_{0}(980) and clues for a new 1^{--} resonance
We study the e^{+}e^{-} to phi pi pi reaction for pions in an isoscalar
s-wave which is dominated by loop mechanisms. For kaon loops we start from the
conventional RCHPT, but use the unitarized amplitude for KbarK-pipi scattering
and the full kaon form factor instead of the lowest order terms. We study also
effects of vector mesons using RCHPT supplemented with the conventional
anomalous term for VVP interactions and taking into account the effects of
heavy vector mesons in the K*K transition form factor. We find a peak in the
dipion invariant mass around the f_{0}(980) as in the experiment. Selecting the
phi f_{0}(980) contribution as a function of the e^{+}e^{-} energy we also
reproduce the experimental data except for a narrow peak, yielding support to
the existence of a 1^{--} resonance above the phi f_{0}(980) threshold,
coupling strongly to this state.Comment: 18 pages, 4 figure
Phonon self-energy corrections to non-zero wavevector phonon modes in single-layer graphene
Phonon self-energy corrections have mostly been studied theoretically and
experimentally for phonon modes with zone-center (q = 0) wave-vectors. Here,
gate-modulated Raman scattering is used to study phonons of a single layer of
graphene (1LG) in the frequency range from 2350 to 2750 cm-1, which shows the
G* and the G'-band features originating from a double-resonant Raman process
with q \not= 0. The observed phonon renormalization effects are different from
what is observed for the zone-center q = 0 case. To explain our experimental
findings, we explored the phonon self-energy for the phonons with non-zero
wave-vectors (q \not= 0) in 1LG in which the frequencies and decay widths are
expected to behave oppositely to the behavior observed in the corresponding
zone-center q = 0 processes. Within this framework, we resolve the
identification of the phonon modes contributing to the G* Raman feature at 2450
cm-1 to include the iTO+LA combination modes with q \not= 0 and the 2iTO
overtone modes with q = 0, showing both to be associated with wave-vectors near
the high symmetry point K in the Brillouin zone
Percolation with long-range correlated disorder
Long-range power-law correlated percolation is investigated using Monte Carlo
simulations. We obtain several static and dynamic critical exponents as
function of the Hurst exponent which characterizes the degree of spatial
correlation among the occupation of sites. In particular, we study the fractal
dimension of the largest cluster and the scaling behavior of the second moment
of the cluster size distribution, as well as the complete and accessible
perimeters of the largest cluster. Concerning the inner structure and transport
properties of the largest cluster, we analyze its shortest path, backbone, red
sites, and conductivity. Finally, bridge site growth is also considered. We
propose expressions for the functional dependence of the critical exponents on
Phase locking dynamics of dipolarly coupled vortex-based spin transfer oscillators
Phase locking dynamics of dipolarly coupled vortices excited by
spin-polarized current in two identical nanopillars is studied as a function of
the interpillar distance L. Numerical study and analytical model have proved
the remarkable efficiency of magneto-static interaction to achieve phase
locking. Investigating the dynamics in the transient regime towards phase
locking, we extract the evolution of the locking time \tau, the coupling
strength {\mu} and the interaction energy W. Finally, we compare this coupling
energy with the one obtained by simple model.Comment: 4 pages, 4 figure
Base manifolds for fibrations of projective irreducible symplectic manifolds
Given a projective irreducible symplectic manifold of dimension , a
projective manifold and a surjective holomorphic map with
connected fibers of positive dimension, we prove that is biholomorphic to
the projective space of dimension . The proof is obtained by exploiting two
geometric structures at general points of : the affine structure arising
from the action variables of the Lagrangian fibration and the structure
defined by the variety of minimal rational tangents on the Fano manifold
Nature of the constant factor in the relation between radial breathing mode frequency and tube diameter for single-wall carbon nanotubes
Resonance Raman scattering is used to determine the radial breathing mode (RBM) frequency (ωRBM) dependence on tube diameter (dt) for single-wall carbon nanotubes (SWNTs). We establish experimentally the ωRBM=227.0/dt as the fundamental relation for pristine SWNTs. All the other RBM values found in the literature can be explained by an upshift in frequency due mostly to van der Waals interaction between SWNTs and environment
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