Smart Contract Templates: foundations, design landscape and research directions

In this position paper, we consider some foundational topics regarding smart contracts (such as terminology, automation, enforceability, and semantics) and define a smart contract as an automatable and enforceable agreement. We explore a simple semantic framework for smart contracts, covering both operational and non-operational aspects, and describe templates and agreements for legally-enforceable smart contracts, based on legal documents. Building upon the Ricardian Contract, we identify operational parameters in the legal documents and use these to connect legal agreements to standardised code. We also explore the design landscape, including increasing sophistication of parameters, increasing use of common standardised code, and long-term research

A new diagrammatic representation for correlation functions in the in-in formalism

In this paper we provide an alternative method to compute correlation functions in the in-in formalism, with a modified set of Feynman rules to compute loop corrections. The diagrammatic expansion is based on an iterative solution of the equation of motion for the quantum operators with only retarded propagators, which makes each diagram intrinsically local (whereas in the standard case locality is the result of several cancellations) and endowed with a straightforward physical interpretation. While the final result is strictly equivalent, as a bonus the formulation presented here also contains less graphs than other diagrammatic approaches to in-in correlation functions. Our method is particularly suitable for applications to cosmology.Comment: 14 pages, matches the published version. includes a modified version of axodraw.sty that works with the Revtex4 clas

Intergenic and intronic DNA hypomethylated regions as putative regulators of imprinted domains

© 2018 2018 Future Medicine Ltd. Aim: To investigate the regulatory potential of intergenic/intronic hypomethylated regions (iHMRs) within imprinted domains. Materials & methods: Based on the preliminary results of the histone modification and conservation profiles, we conducted reporter assays on the Peg3 and H19 domain iHMRs. The in vitro results were confirmed by the in vivo deletion of Peg3-iHMR designed to test its function in the Peg3 imprinted domain. Results & conclusion: Initial bioinformatic analyses suggested that some iHMRs may be noncanonical enhancers for imprinted genes. Consistent with this, Peg3- and H19-iHMRs showed context-dependent promoter and enhancer activity. Further, deletion of Peg3-iHMR resulted in allele- and sex-specific misregulation of several imprinted genes within the domain. Taken together, these results suggest that some iHMRs may function as domain-wide regulators for the associated imprinted domains

Parallel algorithm with spectral convergence for nonlinear integro-differential equations

We discuss a numerical algorithm for solving nonlinear integro-differential equations, and illustrate our findings for the particular case of Volterra type equations. The algorithm combines a perturbation approach meant to render a linearized version of the problem and a spectral method where unknown functions are expanded in terms of Chebyshev polynomials (El-gendi's method). This approach is shown to be suitable for the calculation of two-point Green functions required in next to leading order studies of time-dependent quantum field theory.Comment: 15 pages, 9 figure

1+1 Dimensional Compactifications of String Theory

We argue that stable, maximally symmetric compactifications of string theory to 1+1 dimensions are in conflict with holography. In particular, the finite horizon entropies of the Rindler wedge in 1+1 dimensional Minkowski and anti de Sitter space, and of the de Sitter horizon in any dimension, are inconsistent with the symmetries of these spaces. The argument parallels one made recently by the same authors, in which we demonstrated the incompatibility of the finiteness of the entropy and the symmetries of de Sitter space in any dimension. If the horizon entropy is either infinite or zero the conflict is resolved.Comment: 11 pages, 2 figures v2: added discussion of AdS_2 and comment

Predicting gas-flow distribution in pilot-scale fluidized beds using cfd simulations

Bubbling fluidized beds are used extensively in energy and chemical industries because of their excellent heat and mass transfer characteristics. Recently, CFD has been identified as a useful tool for predicting reactor performance, but application to large scales continues to be challenging because of limitations on computational resources. Given that the hydrodynamics can largely be characterized by bubbles rising through the bed, a more feasible approach for investigating large-scale reactors is to quantify bubble dynamics and specifically, gas distribution in different phases- visible bubble flow, bubble-through flow and dense-phase flow. In this study, 3D CFD simulations of bubbling fluidized beds are first conducted to establish the impact of scale (bed diameter) on the hydrodynamics. Using solids circulation and bubble statistics (1), it is established that wall effects cease to be significant in beds larger than 50 cm (bed aspect ratio less than 1). At this scale, simulations are then carried out for two distinct Geldart B particles and data is subsequently analyzed for gas-flow distribution in the bed. Bubble statistics are also compared with existing correlations and their relation to solids circulation and mixing is investigated. The physical model and numerical tool were developed and validated in previous studies (1,2), while 3D Bubble statistics are computed using MS3DATA (Multiphase Statistics using 3D Detection and Tracking Algorithm) (3). Accurate description of the gas-flow is crucial for large-scale combustor design since quantifying gas distribution will indicate both fuel rich zones as well as oxidant bypass through bubbles leading to inefficient performance. Please click Additional Files below to see the full abstract

Renormalization of initial conditions and the trans-Planckian problem of inflation

Understanding how a field theory propagates the information contained in a given initial state is essential for quantifying the sensitivity of the cosmic microwave background to physics above the Hubble scale during inflation. Here we examine the renormalization of a scalar theory with nontrivial initial conditions in the simpler setting of flat space. The renormalization of the bulk theory proceeds exactly as for the standard vacuum state. However, the short distance features of the initial conditions can introduce new divergences which are confined to the surface on which the initial conditions are imposed. We show how the addition of boundary counterterms removes these divergences and induces a renormalization group flow in the space of initial conditions.Comment: 22 pages, 4 eps figures, uses RevTe

On time-dependent AdS/CFT

We clarify aspects of the holographic AdS/CFT correspondence that are typical of Lorentzian signature, to lay the foundation for a treatment of time-dependent gravity and conformal field theory phenomena. We provide a derivation of bulk-to-boundary propagators associated to advanced, retarded and Feynman bulk propagators, and provide a better understanding of the boundary conditions satisfied by the bulk fields at the horizon. We interpret the subleading behavior of the wavefunctions in terms of specific vacuum expectation values, and compute two-point functions in our framework. We connect our bulk methods to the closed time path formalism in the boundary field theory.Comment: 19 pages, v2: added reference, JHEP versio

Numerical Approximations Using Chebyshev Polynomial Expansions

We present numerical solutions for differential equations by expanding the unknown function in terms of Chebyshev polynomials and solving a system of linear equations directly for the values of the function at the extrema (or zeros) of the Chebyshev polynomial of order N (El-gendi's method). The solutions are exact at these points, apart from round-off computer errors and the convergence of other numerical methods used in connection to solving the linear system of equations. Applications to initial value problems in time-dependent quantum field theory, and second order boundary value problems in fluid dynamics are presented.Comment: minor wording changes, some typos have been eliminate

The Role of Nonequilibrium Dynamical Screening in Carrier Thermalization

We investigate the role played by nonequilibrium dynamical screening in the thermalization of carriers in a simplified two-component two-band model of a semiconductor. The main feature of our approach is the theoretically sound treatment of collisions. We abandon Fermi's Golden rule in favor of a nonequilibrium field theoretic formalism as the former is applicable only in the long-time regime. We also introduce the concept of nonequilibrium dynamical screening. The dephasing of excitonic quantum beats as a result of carrier-carrier scattering is brought out. At low densities it is found that the dephasing times due to carrier-carrier scattering is in picoseconds and not femtoseconds, in agreement with experiments. The polarization dephasing rates are computed as a function of the excited carrier density and it is found that the dephasing rate for carrier-carrier scattering is proportional to the carrier density at ultralow densities. The scaling relation is sublinear at higher densities, which enables a comparison with experiment.Comment: Revised version with additional refs. 12 pages, figs. available upon request; Submitted to Phys. Rev.