7,390 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
Coded Caching based on Combinatorial Designs
We consider the standard broadcast setup with a single server broadcasting
information to a number of clients, each of which contains local storage
(called \textit{cache}) of some size, which can store some parts of the
available files at the server. The centralized coded caching framework,
consists of a caching phase and a delivery phase, both of which are carefully
designed in order to use the cache and the channel together optimally. In prior
literature, various combinatorial structures have been used to construct coded
caching schemes. In this work, we propose a binary matrix model to construct
the coded caching scheme. The ones in such a \textit{caching matrix} indicate
uncached subfiles at the users. Identity submatrices of the caching matrix
represent transmissions in the delivery phase. Using this model, we then
propose several novel constructions for coded caching based on the various
types of combinatorial designs. While most of the schemes constructed in this
work (based on existing designs) have a high cache requirement (uncached
fraction being or , being
the number of users), they provide a rate that is either constant or decreasing
() with increasing , and moreover require competitively
small levels of subpacketization (being ), which is an
extremely important parameter in practical applications of coded caching. We
mark this work as another attempt to exploit the well-developed theory of
combinatorial designs for the problem of constructing caching schemes,
utilizing the binary caching model we develop.Comment: 10 pages, Appeared in Proceedings of IEEE ISIT 201
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
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
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Electrochemical oxidation of ethanol at ruthenium at oxide coated titanium electrode
Electrochemical oxidation of ethanol in 0.5 M sulphuric acid at ruthenium oxide coated titanium electrode was studied. Results of galvanostatic polarization and chronopotentiometric studies are reported. The data indicate the process to be adsorption controlled and accordingly a probable mechanism is propose
Removal of Interferences from Partial Discharge Pulses using Wavelet Transform
It is essential to detect partial discharge (PD) as a symptom of insulation breakdown in high voltage (HV) applications. However accuracy of such measurement is often degraded due to the existence of noise in the signal. Wavelet Transform (WT) seems to be more suitable than traditional Fourier Transform in analyzing signals with interesting transient information such as partial discharge (PD) signals. In this paper a WT method with soft thresholding is used for signal denoising. PD signals and corona obtained from actual measurements with different voltage magnitudes are processed. Processed signals show the better result.
Immunology of occupational lung diseases caused by dust: an overview
The lungs are exposed to numerous injurious substances.Such injury may be the result of immunological or non-immunological mechanisms. The lung clears itself of inhaled particles by means of ciliated cells lining the airways and the macrophages.The latter play an important role in the immune process as well.Inorganic particles are ingested by macrophages and if found inert are transported for eventual expulsion.Particles such as silica are poorly handled by macrophages, they not only damage the macrophages but also impair their function. Others, such as asbestos, may stimulate fibrosis. Endogenous factors such as the presence of auto-antibodies (rheumatoid factor or anti-nuclear factor) alter the response of the host to inhaled particles.The pathological changes caused by handling inorganic dusts include intestitial fibrosis, nodular fibrosis or macule formation leading to emphysema.Occupational asthma a occurs when individuals are exposed to dusts during the course of their work. The lung responds differently to organic dust. T cells and complement are important elements in handling organic dust.The role of inhaled steroids which have no significant systemic effects in the prevention of certain occupational asthmas is worth evaluating, apart from control measures which minimise the exposure
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