163 research outputs found
Adventitious shoot regeneration from leaf explants of the valuable medicinal herb Plectranthus barbatus Andrews
The objective of this study was to develop an efficient protocol for adventitious shoot regeneration for Plectranthus barbatus Andrews using leaf explants. The explants were cultured on MS (Murashige and Skoog, 1962) medium containing various concentration of kinetin (KN), 6-benzylaminopurine (BAP) and thidiazuron (TDZ) (0.5 to 3.0 mg/l) or in combination with á-naphthalene acetic acid (NAA) for shoot development. The highest adventitious shoot regeneration percentage (80%) and average maximum number of 19.7 ± 2.08 shoots per explants was observed on MS medium supplemented with 1.5 mg/l KN followed by 2.0 mg/l BAP with 1.0 mg/l NAA (15.0 ± 2.20 shoots per explants). The shoots were excised and the residual explants were transferred to fresh medium where again they developed shoots. The shoots were elongated when they were cultured on half strength MS medium supplemented with 0.6 mg/l gibberellic acid (GA3) and 0.5 mg/l KN. The in vitro developed shoots produced roots when transferred to half strength MS medium augmented with 1.5 mg/l indole-3-butyric acid (IBA). The in vitro raised plantlets were successfully transferred to mixture of river sand, garden soil and saw dust (1:1:1) and was hardened in controlled environment. Hardened plantlets were transferred to soil in greenhouse.Key words: Plectranthus barbatus, Lamiaceae, medicinal plant, leaf explants, direct organogenesis, in vitro, plant growth regulators
On-Shell Recursion Relations for Generic Theories
We show that on-shell recursion relations hold for tree amplitudes in generic
two derivative theories of multiple particle species and diverse spins. For
example, in a gauge theory coupled to scalars and fermions, any amplitude with
at least one gluon obeys a recursion relation. In (super)gravity coupled to
scalars and fermions, the same holds for any amplitude with at least one
graviton. This result pertains to a broad class of theories, including QCD, N=4
SYM, and N=8 supergravity.Comment: 19 pages, 3 figure
Boundary Contributions Using Fermion Pair Deformation
Continuing the study of boundary BCFW recursion relation of tree level
amplitudes initiated in \cite{Feng:2009ei}, we consider boundary contributions
coming from fermion pair deformation. We present the general strategy for these
boundary contributions and demonstrate calculations using two examples, i.e,
the standard QCD and deformed QCD with anomalous magnetic momentum coupling. As
a by-product, we have extended BCFW recursion relation to off-shell gluon
current, where because off-shell gluon current is not gauge invariant, a new
feature must be cooperated.Comment: 26 pages, 4 figure
Dual conformal constraints and infrared equations from global residue theorems in N=4 SYM theory
Infrared equations and dual conformal constraints arise as consistency
conditions on loop amplitudes in N=4 super Yang-Mills theory. These conditions
are linear relations between leading singularities, which can be computed in
the Grassmannian formulation of N=4 super Yang-Mills theory proposed recently.
Examples for infrared equations have been shown to be implied by global residue
theorems in the Grassmannian picture. Both dual conformal constraints and
infrared equations are mapped explicitly to global residue theorems for
one-loop next-to-maximally-helicity-violating amplitudes. In addition, the
identity relating the BCFW and its parity-conjugated form of tree-level
amplitudes, is shown to emerge from a particular combination of global residue
theorems.Comment: 21 page
Complete Equivalence Between Gluon Tree Amplitudes in Twistor String Theory and in Gauge Theory
The gluon tree amplitudes of open twistor string theory, defined as contour
integrals over the ACCK link variables, are shown to satisfy the BCFW
relations, thus confirming that they coincide with the corresponding amplitudes
in gauge field theory. In this approach, the integration contours are specified
as encircling the zeros of certain constraint functions that force the
appropriate relation between the link variables and the twistor string
world-sheet variables. To do this, methods for calculating the tree amplitudes
using link variables are developed further including diagrammatic methods for
organizing and performing the calculations.Comment: 38 page
General Split Helicity Gluon Tree Amplitudes in Open Twistor String Theory
We evaluate all split helicity gluon tree amplitudes in open twistor string
theory. We show that these amplitudes satisfy the BCFW recurrence relations
restricted to the split helicity case and, hence, that these amplitudes agree
with those of gauge theory. To do this we make a particular choice of the
sextic constraints in the link variables that determine the poles contributing
to the contour integral expression for the amplitudes. Using the residue
theorem to re-express this integral in terms of contributions from poles at
rational values of the link variables, which we determine, we evaluate the
amplitudes explicitly, regaining the gauge theory results of Britto et al.Comment: 30 pages, minor misprints correcte
Generating MHV super-vertices in light-cone gauge
We constructe the SYM lagrangian in light-cone gauge using
chiral superfields instead of the standard vector superfield approach and
derive the MHV lagrangian. The canonical transformations of the gauge field and
gaugino fields are summarised by the transformation condition of chiral
superfields. We show that MHV super-vertices can be described
by a formula similar to that of the MHV super-amplitude. In the
discussions we briefly remark on how to derive Nair's formula for
SYM theory directly from light-cone lagrangian.Comment: 25 pages, 7 figures, JHEP3 style; v2: references added, some typos
corrected; Clarification on the condition used to remove one Grassmann
variabl
Manifest SO(N) invariance and S-matrices of three-dimensional N=2,4,8 SYM
An on-shell formalism for the computation of S-matrices of SYM theories in
three spacetime dimensions is presented. The framework is a generalization of
the spinor-helicity formalism in four dimensions. The formalism is applied to
establish the manifest SO(N) covariance of the on-shell superalgebra relevant
to N =2,4 and 8 SYM theories in d=3. The results are then used to argue for the
SO(N) invariance of the S-matrices of these theories: a claim which is proved
explicitly for the four-particle scattering amplitudes. Recursion relations
relating tree amplitudes of three-dimensional SYM theories are shown to follow
from their four-dimensional counterparts. The results for the four-particle
amplitudes are verified by tree-level perturbative computations and a unitarity
based construction of the integrand corresponding to the leading perturbative
correction is also presented for the N=8 theory. For N=8 SYM, the manifest
SO(8) symmetry is used to develop a map between the color-ordered amplitudes of
the SYM and superconformal Chern-Simons theories, providing a direct connection
between on-shell observables of D2 and M2-brane theories.Comment: 28 page
Spinor Helicity and Dual Conformal Symmetry in Ten Dimensions
The spinor helicity formalism in four dimensions has become a very useful
tool both for understanding the structure of amplitudes and also for practical
numerical computation of amplitudes. Recently, there has been some discussion
of an extension of this formalism to higher dimensions. We describe a
particular implementation of the spinor-helicity method in ten dimensions.
Using this tool, we study the tree-level S-matrix of ten dimensional super
Yang-Mills theory, and prove that the theory enjoys a dual conformal symmetry.
Implications for four-dimensional computations are discussed.Comment: 24 pages, 1 figure
Note on New KLT relations
In this short note, we present two results about KLT relations discussed in
recent several papers. Our first result is the re-derivation of Mason-Skinner
MHV amplitude by applying the S_{n-3} permutation symmetric KLT relations
directly to MHV amplitude. Our second result is the equivalence proof of the
newly discovered S_{n-2} permutation symmetric KLT relations and the well-known
S_{n-3} permutation symmetric KLT relations. Although both formulas have been
shown to be correct by BCFW recursion relations, our result is the first direct
check using the regularized definition of the new formula.Comment: 15 Pages; v2: minor correction
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