4,119 research outputs found
Light-Front Holography, AdS/QCD, and Hadronic Phenomena
AdS/QCD, the correspondence between theories in a modified five-dimensional
anti-de Sitter space and confining field theories in physical space-time,
provides a remarkable semiclassical model for hadron physics. Light-front
holography allows hadronic amplitudes in the AdS fifth dimension to be mapped
to frame-independent light-front wavefunctions of hadrons in physical
space-time, thus providing a relativistic description of hadrons at the
amplitude level. We identify the AdS coordinate with an invariant
light-front coordinate which separates the dynamics of quark and gluon
binding from the kinematics of constituent spin and internal orbital angular
momentum. The result is a single-variable light-front Schr\"odinger equation
with a confining potential which determines the eigenspectrum and the
light-front wavefunctions of hadrons for general spin and orbital angular
momentum. The mapping of electromagnetic and gravitational form factors in AdS
space to their corresponding expressions in light-front theory confirms this
correspondence. Some novel features of QCD are discussed, including the
consequences of confinement for quark and gluon condensates. The distinction
between static structure functions, such as the probability distributions
computed from the square of the light-front wavefunctions, versus dynamical
structure functions which include the effects of rescattering, is emphasized. A
new method for computing the hadronization of quark and gluon jets at the
amplitude level, an event amplitude generator, is outlined.Comment: 11 pages, 3 figures. Talk presented by SJB at Light Cone 2009:
Relativistic Hadronic And Particle Physics, 8-13 Jul 2009, Sao Jose dos
Campos, Brazi
The Impact of QCD and Light-Cone Quantum Mechanics on Nuclear Physics
We discuss a number of novel applications of Quantum Chromodynamics to
nuclear structure and dynamics, such as the reduced amplitude formalism for
exclusive nuclear amplitudes. We particularly emphasize the importance of
light-cone Hamiltonian and Fock State methods as a tool for describing the
wavefunctions of composite relativistic many-body systems and their
interactions. We also show that the use of covariant kinematics leads to
nontrivial corrections to the standard formulae for the axial, magnetic, and
quadrupole moments of nucleons and nuclei.Comment: 25 pages, uuencoded postscript file---To obtain a hard copy of this
paper, send e-mail to [email protected] and ask fo
Light-Front Holography and AdS/QCD Correspondence
Light-Front Holography is a remarkable consequence of the correspondence
between string theory in AdS space and conformal field theories in
physical-space time. It allows string modes in the AdS fifth
dimension to be precisely mapped to the light-front wavefunctions of hadrons in
terms of a specific light-front impact variable which measures the
separation of the quark and gluonic constituents within the hadron. This
mapping was originally obtained by matching the exact expression for
electromagnetic current matrix elements in AdS space with the corresponding
exact expression for the current matrix element using light-front theory in
physical space-time. More recently we have shown that one obtains the identical
holographic mapping using matrix elements of the energy-momentum tensor, thus
providing an important consistency test and verification of holographic mapping
from AdS to physical observables defined on the light-front. The resulting
light-front Schrodinger equations predicted from AdS/QCD give a good
representation of the observed meson and baryon spectra and give excellent
phenomenological predictions for amplitudes such as electromagnetic form
factors and decay constants.Comment: 14 pages. Presented at QCD Down Under II, Auckland, New Zealand,
January 17-19, 200
Applications of AdS/QCD and Light-Front Holography to Baryon Physics
The correspondence between theories in anti-de Sitter space and field
theories in physical space-time leads to an analytic, semiclassical model for
strongly-coupled QCD which has scale invariance at short distances and color
confinement at large distances. These equations, for both mesons and baryons,
give a very good representation of the observed hadronic spectrum, including a
zero mass pion. Light-front holography allows hadronic amplitudes in the AdS
fifth dimension to be mapped to frame-independent light-front wavefunctions of
hadrons in physical space-time, thus providing a relativistic description of
hadrons at the amplitude level. The meson and baryon wavefunctions derived from
light-front holography and AdS/QCD also have remarkable phenomenological
features, including predictions for the electromagnetic form factors and decay
constants. The approach can be systematically improved using light-front
Hamiltonian methods. Some novel features of QCD for baryon physics are also
discussed.Comment: Presented by SJB at the International Conference on the Structure of
Baryons, BARYONS'10, December 7-11, 2010, Osaka, Japa
Nearly Conformal QCD and AdS/CFT
The AdS/CFT correspondence is a powerful tool to study the properties of
conformal QCD at strong coupling in terms of a higher dimensional dual gravity
theory. The power-law falloff of scattering amplitudes in the non-perturbative
regime and calculable hadron spectra follow from holographic models dual to QCD
with conformal behavior at short distances and confinement at large distances.
String modes and fluctuations about the AdS background are identified with QCD
degrees of freedom and orbital excitations at the AdS boundary limit. A
description of form factors in space and time-like regions and the behavior of
light-front wave functions can also be understood in terms of a dual gravity
description in the interior of AdS.Comment: 8 pages, LateX, 3 figures. Presented at First Workshop on
Quark-Hadron Duality and the Transition to pQCD, Frascati, Italy, 6-8 June
2005. AdS LFWF mapping reexamine
Hadron Spectroscopy and Wavefunctions in QCD and the AdS/CFT Correspondence
The AdS/CFT correspondence has led to important insights into the properties
of quantum chromodynamics even though QCD is a broken conformal theory. A
holographic model based on a truncated AdS space can be used to obtain the
hadronic spectrum of light and bound states. Specific
hadrons are identified by the correspondence of string modes with the dimension
of the interpolating operator of the hadron's valence Fock state, including
orbital angular momentum excitations. The predicted mass spectrum is linear at high orbital angular momentum. Since only one parameter, the QCD
scale , is introduced, the agreement with the pattern of
physical states is remarkable. In particular, the ratio of to nucleon
trajectories is determined by the ratio of zeros of Bessel functions. One can
also use the extended AdS/CFT space-time theory to obtain a model for hadronic
light-front wavefunctions, thus providing a relativistic description of hadrons
in QCD at the amplitude level. The model wavefunctions display confinement at
large inter-quark separation and conformal symmetry at short distances. In
particular, the scaling and conformal properties of the LFWFs at high relative
momenta agree with perturbative QCD. These AdS/CFT model wavefunctions could be
used as an initial ansatz for a variational treatment of the light-front QCD
Hamiltonian. Hadron form factors in both the space-like and time-like regions
are also predicted.Comment: Invited Talk, presented presented at the XI. International Conference
on Hadron Spectroscopy--HADRON 05,Rio de Janeiro, Brazil, 21-26 August 200
Excited Baryons in Holographic QCD
The light-front holographic QCD approach is used to describe baryon
spectroscopy and the systematics of nucleon transition form factors.Comment: Invited talk presented by GdT at NSTAR 2011, the 8th International
Workshop on the Physics of Excited Nucleons, Jefferson Laboratory, May 17 -
20, 201
- …