14,265 research outputs found
Comments on Worldsheet Description of the Omega Background
Nekrasov's partition function is defined on a flat bundle of R^4 over S^1
called the Omega background. When the fibration is self-dual, the partition
function is known to be equal to the topological string partition function,
which computes scattering amplitudes of self-dual gravitons and graviphotons in
type II superstring compactified on a Calabi-Yau manifold. We propose a
generalization of this correspondence when the fibration is not necessarily
self-dual.Comment: 11 page
The Stoyanovsky-Ribault-Teschner Map and String Scattering Amplitudes
Recently, Ribault and Teschner pointed out the existence of a one-to-one
correspondence between N-point correlation functions for the SL(2,C)_k/SU(2)
WZNW model on the sphere and certain set of 2N-2-point correlation functions in
Liouville field theory. This result is based on a seminal work by Stoyanovsky.
Here, we discuss the implications of this correspondence focusing on its
application to string theory on curved backgrounds. For instance, we analyze
how the divergences corresponding to worldsheet instantons in AdS_3 can be
understood as arising from the insertion of the dual screening operator in the
Liouville theory side. We also study the pole structure of N-point functions in
the 2D Euclidean black hole and its holographic meaning in terms of the Little
String Theory. This enables us to interpret the correspondence between CFTs as
encoding a LSZ-type reduction procedure. Furthermore, we discuss the scattering
amplitudes violating the winding number conservation in those backgrounds and
provide a formula connecting such amplitudes with observables in Liouville
field theory. Finally, we study the WZNW correlation functions in the limit k
-> 0 and show that, at the point k=0, the Stoyanovsky-Ribault-Teschner
dictionary turns out to be in agreement with the FZZ conjecture at a particular
point of the space of parameters where the Liouville central charge becomes
c=-2. This result makes contact with recent studies on the dynamical tachyon
condensation in closed string theory.Comment: 30 pages; no figure
Low-scale Supersymmetry from Inflation
We investigate an inflation model with the inflaton being identified with a
Higgs boson responsible for the breaking of U(1)B-L symmetry. We show that
supersymmetry must remain a good symmetry at scales one order of magnitude
below the inflation scale, in order for the inflation model to solve the
horizon and flatness problems, as well as to account for the observed density
perturbation. The upper bound on the soft supersymmetry breaking mass lies
between 1TeV and 10^3TeV. Interestingly, our finding opens up a possibility
that universes with the low-scale supersymmetry are realized by the
inflationary selection. Our inflation model has rich implications; non-thermal
leptogenesis naturally works, and the gravitino and moduli problems as well as
the moduli destabilization problem can be solved or ameliorated; the
standard-model higgs boson receives a sizable radiative correction if the
supersymmertry breaking takes a value on the high side ~10^3TeV.Comment: 23pages, 3 figures. v2: references adde
Refined topological amplitudes in N=1 flux compactification
We study the implication of refined topological string amplitudes in the
supersymmetric N=1 flux compactification. They generate higher derivative
couplings among the vector multiplets and graviphoton with generically
non-holomorphic moduli dependence. For a particular term, we can compute them
by assuming the geometric engineering. We claim that the Dijkgraaf-Vafa large N
matrix model with the beta-ensemble measure directly computes the higher
derivative corrections to the supersymmetric effective action of the
supersymmetric N=1$ gauge theory.Comment: 16 pages, v2: reference adde
Plasmonic nanoparticle enhanced light absorption in GaAs solar cells
We demonstrate an improvement in efficiency of optically thin GaAs solar cells decorated with size-controlled Ag nanoparticles fabricated by masked deposition through anodic aluminum oxide templates. The strong scattering by the interacting surface plasmons in densely formed high aspect-ratio nanoparticles effectively increases the optical path of the incident light in the absorber layers resulting in an 8% increase in the short circuit current density of the cell. The nanoparticle array sheet conductivity also reduces the cell surface sheet resistance evidenced by an improved fill factor. This dual function of plasmonic nanoparticles has potential to enable thinner photovoltaic layers in solar cells
The Hamilton-Jacobi Equations for Strings and p-Branes
Simple derivation of the Hamilton-Jacobi equation for bosonic strings and
p-branes is given. The motion of classical strings and p-branes is described by
two and p+1 local fields, respectively. A variety of local field equations
which reduce to the Hamilton-Jacobi equation in the classical limit are given.
They are essentially nonlinear, having no linear term.Comment: 7 page
Strong Electron Confinement By Stacking-fault Induced Fractional Steps on Ag(111) Surfaces
The electron reflection amplitude at stacking-fault (SF) induced
fractional steps is determined for Ag(111) surface states using a low
temperature scanning tunneling microscope. Unexpectedly, remains as high as
as energy increases from 0 to 0.5 eV, which is in clear contrast
to its rapidly decreasing behavior for monatomic (MA) steps [L. B{\"u}rgi et
al., Phys. Rev. Lett. \textbf{81}, 5370 (1998)]. Tight-binding calculations
based on {\em ab-initio} derived band structures confirm the experimental
finding. Furthermore, the phase shifts at descending SF steps are found to be
systematically larger than counterparts for ascending steps by . These results indicate that the subsurface SF plane significantly
contributes to the reflection of surface states
Baryon Asymmetry in a Heavy Moduli Scenario
In some models of supersymmetry breaking, modulus fields are heavy enough to
decay before BBN. But the large entropy produced via moduli decay significantly
dilutes the preexisting baryon asymmetry of the universe. We study whether
Affleck-Dine mechanism can provide enough baryon asymmetry which survives the
dilution, and find several situations in which desirable amount of baryon
number remains after the dilution. The possibility of non-thermal dark matter
is also discussed. This provides the realistic cosmological scenario with heavy
moduli.Comment: 36 pages, 5 figures; added a reference; v3: minor correction
B-mode polarization induced by gravitational waves from kinks on infinite cosmic strings
We investigate the effect of the stochastic gravitational wave (GW)
background produced by kinks on infinite cosmic strings, whose spectrum was
derived in our previous work, on the B-mode power spectrum of the cosmic
microwave background (CMB) anisotropy. We find that the B-mode polarization due
to kinks is comparable to that induced by the motion of the string network and
hence the contribution of GWs from kinks is important for estimating the B-mode
power spectrum originating from cosmic strings. If the tension of cosmic
strings \mu is large enough i.e., G\mu >~ 10^{-8}, B-mode polarization induced
by cosmic strings can be detected by future CMB experiments.Comment: 13 pages, 1 figur
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