590 research outputs found
Towards a Finite- Hologram
We suggest that holographic tensor models related to SYK are viable
candidates for exactly (ie., non-perturbatively in ) solvable holographic
theories. The reason is that in these theories, the Hilbert space is a spinor
representation, and the Hamiltonian (at least in some classes) can be arranged
to commute with the Clifford level. This makes the theory solvable level by
level. We demonstrate this for the specific case of the uncolored
tensor model with arbitrary even , and reduce the question of determining
the spectrum and eigenstates to an algebraic equation relating Young tableaux.
Solving this reduced problem is conceptually trivial and amounts to matching
the representations on either side, as we demonstrate explicitly at low levels.
At high levels, representations become bigger, but should still be tractable.
None of our arguments require any supersymmetry.Comment: 16 page
Contrasting SYK-like Models
We contrast some aspects of various SYK-like models with large- melonic
behavior. First, we note that ungauged tensor models can exhibit symmetry
breaking, even though these are 0+1 dimensional theories. Related to this, we
show that when gauged, some of them admit no singlets, and are anomalous. The
uncolored Majorana tensor model with even is a simple case where gauge
singlets can exist in the spectrum. We outline a strategy for solving for the
singlet spectrum, taking advantage of the results in arXiv:1706.05364, and
reproduce the singlet states expected in . In the second part of the
paper, we contrast the random matrix aspects of some ungauged tensor models,
the original SYK model, and a model due to Gross and Rosenhaus. The latter,
even though disorder averaged, shows parallels with the Gurau-Witten model. In
particular, the two models fall into identical Andreev ensembles as a function
of . In an appendix, we contrast the (expected) spectra of AdS quantum
gravity, SYK and SYK-like tensor models, and the zeros of the Riemann Zeta
function.Comment: 45 pages, 17 figures; v2: minor improvements and rearrangements, refs
adde
Massive Scattering Amplitudes in Six Dimensions
We show that a natural spinor-helicity formalism that can describe massive
scattering amplitudes exists in dimensions. This is arranged by having
helicity spinors carry an index in the Dirac spinor {\bf 4} of the massive
little group, . In the high energy limit, two separate kinds
of massless helicity spinors emerge as required for consistency with
arXiv:0902.0981, with indices in the two 's of the massless little group
. The tensors of lead to particles with arbitrary spin, and
using these and demanding consistent factorization, we can fix and
point tree amplitudes of arbitrary masses and spins: we provide examples.
We discuss the high energy limit of scattering amplitudes and the Higgs
mechanism in this language, and make some preliminary observations about
massive BCFW recursion.Comment: 37 pages; v2: minor improvements, JHEP versio
When Plasmonic Colloids Meet Optical Vortices -- A Brief Review
Structured light has emerged as an important tool to interrogate and
manipulate matter at micron and sub-micron scale. One form of structured light
is an optical vortex beam. The helical wavefront of these vortices carry
orbital angular momentum which can be transferred to a Brownian colloid. When
the colloid is made of metallic nanostructures, such as silver and gold,
resonant optical effects play a vital role, and the interaction leads to
complex dynamics and assembly. This brief review aims to discuss some recent
work on trapping plasmonic colloids with optical vortices and their lattices.
The role of optical scattering and absorption has important implications on the
underlying forces and torques, which is specifically enunciated. The effect of
spin and orbital angular momentum in an optical vortex can lead to spin-orbit
coupling dynamics, and these effects are highlighted with examples from the
literature. In addition to assembly and dynamics, enhanced Brownian motion of
plasmonic colloids under the influence of a vortex-lattice is discussed. The
pedagogical aspects to understand the interaction between optical vortex and
plasmonic colloids is emphasized.Comment: Comments welcome. Invited review article (150 references). Submitted
to Indian Journal of Physics and Applied Physics (IJPAP) - special issue on
nanophotonic
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