Combinatorics and formal geometry of the master equation

We give a general treatment of the master equation in homotopy algebras and describe the operads and formal differential geometric objects governing the corresponding algebraic structures. We show that the notion of Maurer-Cartan twisting is encoded in certain automorphisms of these universal objects

Holographic data storage in a DX-center material

We report on the optical storage of digital data in a semiconductor sample containing DX centers. The diffraction efficiency and the bit-error-rate performance of multiplexed data images are shown to agree well with a simple model of the material. Uniform storage without an exposure schedule is demonstrated. The volume sensitivity is found to be ~10^3 times that of LiNBO3:Fe. The importance of coherent addition of scattered light with diffracted light in holographic data storage is discussed

Participation And performance In 8.02x Electricity And Magnetism: The First Physics MOOC From MITx

Massive Open Online Courses are an exciting new avenue for instruction and research, yet they are full of unknowns. In the Spring of 2013, MITx released its first introductory physics MOOC through the edX platform, generating a total enrollment of 43,000 students from around the world. We describe the population of participants in terms of their age, gender, level of education, and country of origin, highlighting both the diversity of 8.02x enrollees as well as gender gap and retention. Using three midterm exams and the final as waypoints, we highlight performance by different demographic subpopulations and their retention rates. Our work is generally aimed at making a bridge between available MOOC data and topics associated with the Physics Education Research community.Comment: 4 pages, 5 figures, Accepted for publication in the Physics Education Research Conference Proceedings, Portland OR 201

Fast Quantum Search Algorithms in Protein Sequence Comparison - Quantum Biocomputing

Quantum search algorithms are considered in the context of protein sequence comparison in biocomputing. Given a sample protein sequence of length m (i.e m residues), the problem considered is to find an optimal match in a large database containing N residues. Initially, Grover's quantum search algorithm is applied to a simple illustrative case - namely where the database forms a complete set of states over the 2^m basis states of a m qubit register, and thus is known to contain the exact sequence of interest. This example demonstrates explicitly the typical O(sqrt{N}) speedup on the classical O(N) requirements. An algorithm is then presented for the (more realistic) case where the database may contain repeat sequences, and may not necessarily contain an exact match to the sample sequence. In terms of minimizing the Hamming distance between the sample sequence and the database subsequences the algorithm finds an optimal alignment, in O(sqrt{N}) steps, by employing an extension of Grover's algorithm, due to Boyer, Brassard, Hoyer and Tapp for the case when the number of matches is not a priori known.Comment: LaTeX, 5 page

Approximate quantum error correction can lead to better codes

We present relaxed criteria for quantum error correction which are useful when the specific dominant noise process is known. These criteria have no classical analogue. As an example, we provide a four-bit code which corrects for a single amplitude damping error. This code violates the usual Hamming bound calculated for a Pauli description of the error process, and does not fit into the GF(4) classification.Comment: 7 pages, 2 figures, submitted to Phys. Rev.

Fast Shocks From Magnetic Reconnection Outflows

Magnetic reconnection is commonly perceived to drive flow and particle acceleration in flares of solar, stellar, and astrophysical disk coronae but the relative roles of different acceleration mecha- nisms in a given reconnection environment are not well understood. We show via direct numerical simulations that reconnection outflows produce weak fast shocks, when conditions for fast recon- nection are met and the outflows encounter an obstacle. The associated compression ratios lead to a Fermi acceleration particle spectrum that is significantly steeper than the strong fast shocks commonly studied, but consistent with the demands of solar flares. While this is not the only acceleration mechanism operating in a reconnection environment, it is plausibly a ubiquitous one

Electrokinetic-potential fluctuations produced by pipe-flow turbulence

CER62HC-JEC47.July 1964.The distribution across a pipe of turbulent intensities, shearing stress, and energy spectra are inferred from measured electrokinetic-potential fluctuations in a fully developed flow of distilled water in a 2.54 cm diameter glass pipe. These quantities are shown to be in good agreement with those obtained by Laufer and Sandborn with hot-wire anemometers for air flows at the same mean Reynolds number. A tentative analytical model of the phenomena is constructed and analyzed by Maxwell's electrodynamic field equations for a nonmagnetized medium moving with a velocity which is much smaller than the velocity of light. A set of equations governing the interrelation between the electrokinetic- potential fluctuations and the turbulent velocity-fluctuation components of the flow field in fully developed pipe flow is deduced. The equations are simplified and assumed to have the form: σ▽ѱ = ρu. Fourier transforms are then introduced and simple relations between the electrokinetic-potential fluctuations and velocity fluctuations are obtained

Power law profiles in thermally stratified shear flows

CER69-70-HC-JEC-19.December 1969.Includes bibliographical references (page 12).Prepared for U.S. Army Research Grant DA-AMC-28-043-65-G20.A "power law'' model is used to describe the wind and temperature profiles in thermally stratified shear flows for bulk Richardson numbers from - 0.8 to 0.2. It is shown that the power of wind and temperature profiles were not independent of the thermal stability and that similarity between wind and temperature profiles is good. Functional dependence of the power upon the thermal stability is shown for data of Prairie Grass and laboratory measurements.Under grant DA-AMC-28-043-65-G20