5,734 research outputs found
Regge Closed String Scattering and its Implication on Fixed angle Closed String Scattering
We calculate the complete closed string high energy scattering amplitudes
(HSA) in the Regge regime for arbitrary mass levels. As an application, we
deduce the complete ratios among closed string HSA in the fixed angle regime by
using Stirling number identities. These results are in contrast with the
incomplete set of closed string HSA in the fixed angle regime calculated
previously. The complete forms of the fixed angle amplitudes, and hence the
ratios, were not calculable previously without the input of zero-norm state
calculation. This is mainly due to the lack of saddle point in the fixed angle
closed string calculation.Comment: 10 pages. v2: typos correcte
EPR entanglement strategies in two-well BEC
Criteria suitable for measuring entanglement between two different potential
wells in a Bose- Einstein condensation (BEC) are evaluated. We show how to
generate the required entanglement, utilizing either an adiabatic two-mode or
dynamic four-mode interaction strategy, with techniques that take advantage of
s-wave scattering interactions to provide the nonlinear coupling. The dynamic
entanglement method results in an entanglement signature with spatially
separated detectors, as in the Einstein-Podolsky-Rosen (EPR) paradox.Comment: 4 pages, 4 figure
Note on Plane Wave Quantum Mechanics
We study the quantum mechanics of BMN operators with two scalar impurities
and arbitrarily many traces, at one loop and all genus. We prove an operator
identity which partially elucidates the structure of this quantum mechanics,
provides some support for a conjectured formula for the free all genus
two-point functions, and demonstrates that a single O(g_2^2) contact term
arises in the Hamiltonian as a result of transforming from the natural gauge
theory basis to the string basis. We propose to identify the S-matrix of this
quantum mechanics with the S-matrix of string theory in the plane-wave
background.Comment: (22 pages, harvmac) v2: minor change
The Spectrum of the Neumann Matrix with Zero Modes
We calculate the spectrum of the matrix M' of Neumann coefficients of the
Witten vertex, expressed in the oscillator basis including the zero-mode a_0.
We find that in addition to the known continuous spectrum inside [-1/3,0) of
the matrix M without the zero-modes, there is also an additional eigenvalue
inside (0,1). For every eigenvalue, there is a pair of eigenvectors, a
twist-even and a twist-odd. We give analytically these eigenvectors as well as
the generating function for their components. Also, we have found an
interesting critical parameter b_0 = 8 ln 2 on which the forms of the
eigenvectors depend.Comment: 25+1 pages, 3 Figures; typos corrected and some comments adde
BMN Gauge Theory as a Quantum Mechanical System
We rigorously derive an effective quantum mechanical Hamiltonian from N=4
gauge theory in the BMN limit. Its eigenvalues yield the exact one-loop
anomalous dimensions of scalar two-impurity BMN operators for all genera. It is
demonstrated that this reformulation vastly simplifies computations. E.g. the
known anomalous dimension formula for genus one is reproduced through a
one-line calculation. We also efficiently evaluate the genus two correction,
finding a non-vanishing result. We comment on multi-trace two-impurity
operators and we conjecture that our quantum-mechanical reformulation could be
extended to higher quantum loops and more impurities.Comment: 13 pages, v2: minor changes, v3: typo corrected, to appear in Phys.
Lett.
Decay Modes of Unstable Strings in Plane-Wave String Field Theory
The cubic interaction vertex of light-cone string field theory in the
plane-wave background has a simple effective form when considering states with
only bosonic excitations. This simple effective interaction vertex is used in
this paper to calculate the three string interaction matrix elements for states
of arbitrary bosonic excitation and these results are used to examine certain
decay modes on the mass-shell. It is shown that the matrix elements of one
string to two string decays involving only bosonic excitations will vanish to
all orders in 1/mu on the mass-shell when the number of excitations on the
initial string is less than or equal to two, but in general will not vanish
when the number of excitations is greater than two. Also, a truncated
calculation of the mass-shell matrix elements for one string to three string
decays of two excitation states is performed and suggests that these matrix
elements do not vanish on the mass-shell. There is, however, a quantitative
discrepancy between this last result and its (also non-vanishing) gauge theory
prediction from the BMN correspondence.Comment: 11 pages; v2: references added; v3: normalization of interaction
vertex and corresponding amplitudes changed by a factor of mu to reflect SFT
normalization (must now divide by mu to compare with BMN dual gauge theory),
and minor errors correcte
Zero Modes in Electromagnetic Form Factors of the Nucleon in a Light-Cone Diquark Model
We use a diquark model of the nucleon to calculate the electromagnetic form
factors of the nucleon described as a scalar and axialvector diquark bound
state. We provide an analysis of the zero-mode contribution in the diquark
model. We find there are zero-mode contributions to the form factors arising
from the instantaneous part of the quark propagator, which cannot be neglected
compared with the valence contribution but can be removed by the choice of wave
function. We also find that the charge and magnetic radii and magnetic moment
of the proton can be reproduced, while the magnetic moment of the neutron is
too small. The dipole shape of the form factors, and
can be reproduced. The ratio decreases
with but too fast.Comment: 22 pages, 6 pages, accepted by J.Phys.
Fair ways to share benefits from community forests? How commodification is associated with reduced preference for equality and poverty alleviation
This research is concerned with the trend towards commodification of forestry, in the context of community forest governance for sustainable development in the tropics. In these contexts, commodification takes different forms, including sales of certified timbers and sales of carbon credits. In addition to the general aim to enhance income, these market-based forestry interventions typically aim to align with sustainable development agendas, including a) safeguarding ecological integrity and b) promoting poverty alleviation. Our concern here is that the process of forest commodification might lead to a shift in local norms of benefit-sharing, in ways that can hinder these key components of sustainable development goals. We report the results of a survey (N=519) conducted across sites in Bolivia, China and Tanzania that shows that switching from non-monetary to monetary benefits is associated with changes in preferences for distributional fairness in ways that may be detrimental to the poor. In particular, we show that forest commodification is associated with a lower likelihood of of selecting pro-poor or egalitarian approaches to benefit sharing and higher likelihood of selecting to distribute benefits in a way that rewards individual contributions or compensates losses
SYM Description of PP-wave String Interactions: Singlet Sector and Arbitrary Impurities
We study string interactions among string states with arbitrary impurities in
the Type IIB plane wave background using string field theory. We reproduce all
string amplitudes from gauge theory by computing matrix elements of the
dilatation operator in a previously proposed basis of states. A direct
correspondence is found between the string field theory and gauge theory
Feynman diagrams.Comment: 51 pages, 8 figures. Some clarifications added, minor typos correcte
Learning Flow-based Feature Warping for Face Frontalization with Illumination Inconsistent Supervision
Despite recent advances in deep learning-based face frontalization methods,
photo-realistic and illumination preserving frontal face synthesis is still
challenging due to large pose and illumination discrepancy during training. We
propose a novel Flow-based Feature Warping Model (FFWM) which can learn to
synthesize photo-realistic and illumination preserving frontal images with
illumination inconsistent supervision. Specifically, an Illumination Preserving
Module (IPM) is proposed to learn illumination preserving image synthesis from
illumination inconsistent image pairs. IPM includes two pathways which
collaborate to ensure the synthesized frontal images are illumination
preserving and with fine details. Moreover, a Warp Attention Module (WAM) is
introduced to reduce the pose discrepancy in the feature level, and hence to
synthesize frontal images more effectively and preserve more details of profile
images. The attention mechanism in WAM helps reduce the artifacts caused by the
displacements between the profile and the frontal images. Quantitative and
qualitative experimental results show that our FFWM can synthesize
photo-realistic and illumination preserving frontal images and performs
favorably against the state-of-the-art results.Comment: ECCV 2020. Code is available at: https://github.com/csyxwei/FFW
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