Light front holography
In strong interaction physics, light front holography or light front holographic QCD is an approximate version of the theory of quantum chromodynamics (QCD) which results from mapping the gauge theory of QCD to a higher-dimensional anti-de Sitter space (AdS) inspired by the AdS/CFT correspondence[1] (gauge/gravity duality) proposed for string theory.
This procedure makes it possible to find analytic solutions (closed-form expression) in situations where strong coupling occurs (the "strongly coupled regime"), improving predictions of the masses of hadrons (such as protons, neutrons, and mesons) and their internal structure revealed by high-energy accelerator experiments.
[2][3] One of the key problems in elementary particle physics is to compute the mass spectrum and structure of hadrons, such as the proton, as bound states of quarks and gluons.
The most successful theoretical approach has been to formulate QCD as a lattice gauge theory[2] and employ large numerical simulations on advanced computers.
Notwithstanding, important dynamical QCD properties in Minkowski space-time are not amenable to Euclidean numerical lattice computations.
[3] An important theoretical goal is thus to find an initial approximation to QCD which is both analytically tractable and which can be systematically improved.
To address this problem, the light front holography approach maps a confining gauge theory quantized on the light front[4] to a higher-dimensional anti-de Sitter space (AdS) incorporating the AdS/CFT correspondence[1] as a useful guide.
The AdS/CFT correspondence is an example of the holographic principle, since it relates gravitation in a five-dimensional AdS space to a conformal quantum field theory at its four-dimensional space-time boundary.
Light front quantization was introduced by Paul Dirac to solve relativistic quantum field theories.
It is the ideal framework to describe the structure of the hadrons in terms of their constituents measured at the same light-front time,
[5] The interrelation of the AdS geometrical representation with light-front holography provides a remarkable first approximation for the mass spectra and wave functions of meson and baryon light-quark bound states.
[6] Light front holographic methods were originally found by Stanley J. Brodsky and Guy F. de Téramond in 2006 by mapping the electric charge[7] and inertia[8] distributions from the quark currents and the stress–energy tensor[9] of the fundamental constituents within a hadron in AdS[10][11] to physical space time[12][13] using light-front theory.
[18] From this equation, we can map the dynamics of quarks and gluons within hadrons to a higher-dimensional anti-de Sitter (AdS) space.
is derived from the warp factor which modifies the AdS geometry and breaks its conformal invariance.
