Medipix3 Demonstration and understanding of near ideal detector performance for 60 & 80 keV electrons

In our article we report first quantitative measurements of imaging performance for the current generation of hybrid pixel detector, Medipix3, as direct electron detector. Utilising beam energies of 60 & 80 keV, measurements of modulation transfer function (MTF) and detective quantum efficiency (DQE) have revealed that, in single pixel mode (SPM), energy threshold values can be chosen to maximize either the MTF or DQE, obtaining values near to, or even exceeding, those for an ideal detector. We have demonstrated that the Medipix3 charge summing mode (CSM) can deliver simultaneous, near ideal values of both MTF and DQE. To understand direct detection performance further we have characterized the detector response to single electron events, building an empirical model which can predict detector MTF and DQE performance based on energy threshold. Exemplifying our findings we demonstrate the Medipix3 imaging performance, recording a fully exposed electron diffraction pattern at 24-bit depth and images in SPM and CSM modes. Taken together our findings highlight that for transmission electron microscopy performed at low energies (energies <100 keV) thick hybrid pixel detectors provide an advantageous and alternative architecture for direct electron imagin

M-Theory in the Gaugeon Formalism

In this paper we will analyse the Aharony-Bergman-Jafferis-Maldacena (ABJM) theory in $\mathcal{N}=1$ superspace formalism. We then study the quantum gauge transformations for this ABJM theory in gaugeon formalism. We will also analyse the extended BRST symmetry for this ABJM theory in gaugeon formalism and show that these BRST transformations for this theory are nilpotent and this in turn leads to the unitary evolution of the $\mathcal{S}$-matrix.Comment: 8 pages, 0 figures, accepted for publication in Comm. Theor. Phy

Physical equivalence between the covariant and physical graviton two-point functions in de Sitter spacetime

It is known that the covariant graviton two-point function in de Sitter spacetime is infrared divergent for some choices of gauge parameters. On the other hand it is also known that there are no infrared divergences requiring an infrared cutoff for the physical graviton two-point function for this spacetime in the transverse-traceless-synchronous gauge in the global coordinate system. We show in this paper that the covariant graviton Wightman two-point function with two gauge parameters is equivalent to the physical one in the global coordinate system in the sense that they produce the same two-point function of any local gauge-invariant tensor linear in the graviton field such as the linearized Weyl tensor. This confirms the fact, pointed out decades ago, that the infrared divergences of the graviton two-point function in the covariant gauge for some choices of gauge parameters are gauge artifact in the sense that they do not contribute to the Wightman two-point function of any local gauge invariant tensor field in linearized theory.Comment: 33 pages (Revtex), no figures, misprints corrected, reference adde

Harmonic Superspace Gaugeon Formalism for the ABJM Theory

In this paper we will analyse the ABJM theory in harmonic superspace. The harmonic superspace variables will be parameterized by the coset $SU(2)/U(1)$ and thus will have manifest $\mathcal{N} =3$ supersymmetry. We will study the quantum gauge transformations and the BRST transformations of this theory in gaugeon formalism. We will use this BRST symmetry to project out the physical sub-space from the total Hilbert space. We will also show that the evolution of the $\mathcal{S}$-matrix is unitary for this ABJM theory in harmonic superspace.Comment: 11, pages, 0 figures, accepted for publication in Mod. Phys. Lett.

Dynamics in a noncommutative phase space

Dynamics has been generalized to a noncommutative phase space. The noncommuting phase space is taken to be invariant under the quantum group $GL_{q,p}(2)$. The $q$-deformed differential calculus on the phase space is formulated and using this, both the Hamiltonian and Lagrangian forms of dynamics have been constructed. In contrast to earlier forms of $q$-dynamics, our formalism has the advantage of preserving the conventional symmetries such as rotational or Lorentz invariance.Comment: LaTeX-twice, 16 page

Deformation of the ABJM Theory

In this paper we analyse the ABJM theory on deformed spacetime. We show that this theory reduces to a deformed super-Yang-Mills theory when one of the scalar superfields is given a non-vanishing vacuum expectation value. Our analyse is done in N=1 superspace formulism.Comment: 10 pages, 0 figures, accepted for publication in EP

Fast Differentially Private Matrix Factorization

Differentially private collaborative filtering is a challenging task, both in terms of accuracy and speed. We present a simple algorithm that is provably differentially private, while offering good performance, using a novel connection of differential privacy to Bayesian posterior sampling via Stochastic Gradient Langevin Dynamics. Due to its simplicity the algorithm lends itself to efficient implementation. By careful systems design and by exploiting the power law behavior of the data to maximize CPU cache bandwidth we are able to generate 1024 dimensional models at a rate of 8.5 million recommendations per second on a single PC