Invariant hyperkahler structures on the cotangent bundles of Hermitian symmetric spaces

Let $G/K$ be an irreducible Hermitian symmetric spaces of compact type with the standard homogeneous complex structure. Then the real symplectic manifold $(T^*(G/K),\Omega)$ has the natural complex structure $J^-$. We construct all $G$-invariant K\"ahler structures $(J,\Omega)$ on homogeneous domains in $T^*(G/K)$ anticommuting with $J^-$. Each such a hypercomplex structure, together with a suitable metric, defines a hyperk\"ahler structure. As an application, we obtain a new proof of the Harish-Chandra and Moore theorem.Comment: 24 pages, AMSTEX,some offprints and the proof of Lemma 4.10 are correcte

Hermitian Calabi functional in complexified orbits

Let $(M,\omega)$ be a compact symplectic manifold. We denote by \ac the space of all almost complex structure compatible with $\omega$. \ac has a natural foliation structure with the complexified orbit as leaf. We obtain an explicit formula of the Hessian of Hermitian Calabi functional at an extremal almost K\"ahler metric in \ac. We prove that the Hessian of Hermitian Calabi functional is semi-positive definite at critical point when restricted to a complexified orbit, as corollaries we obtain some results analogy to K\"ahler case. We also show weak parabolicity of the Hermitian Calabi flow

Unified formalism for Palatini gravity

This paper is devoted to the construction of a unified formalism for Palatini and unimodular gravity. The idea is to employ a relationship between unified formalism for a Griffiths variational problem and its classical Lepage-equivalent variational problem. The main geometrical tools involved in these constructions are canonical forms living on the first jet of the frame bundle for the spacetime manifold. These forms play an essential role in providing a global version of the Palatini Lagrangian and expressing the metricity condition in an invariant form. With them, we were able to find the associated equations of motion in invariant terms and, by using previous results from the literature, to prove their involutivity. As a bonus, we showed how this construction can be used to provide a unified formalism for the so-called unimodular gravity by employing a reduction of the structure group of the frame bundle to the special linear group.Fil: Capriotti, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Matemática; Argentin

Translesion synthesis DNA polymerase η exhibits a specific RNA extension activity and a transcription-associated function

We thank Andres Aguilera for providing the pCYC-LacZ plasmid for the GLRO experiments, and Szilvia Minorits for technical assistance. This work was also supported by grants from the National Research, Development and Innovation Office: GINOP-2.3.2-15-2016-00001 and GINOP-2.3.2-15-2016-00024.Peer reviewedPublisher PD

On some aspects of casual and neutral equations used in mathematical modelling

The problem that motivates the considerations here is the construction of mathematical models of natural phenomena that depend upon past states. The paper divides naturally into two parts: in the first, we expound the inter-connection between ordinary differential equations, delay differential equations, neutral delay-differential equations and integral equations (with emphasis on certain linear cases). As we show, this leads to a natural hierarchy of model complexity when such equations are used in mathematical and computational modelling, and to the possibility of reformulating problems either to facilitate their numerical solution or to provide mathematical insight, or both. Volterra integral equations include as special cases the others we consider. In the second part, we develop some practical and theoretical consequences of results given in the first part. In particular, we consider various approaches to the definition of an adjoint, we establish (notably, in the context of sensitivity analysis for neutral delay-differential equations) roles for well-defined ad-joints and ‘quasi-adjoints’, and we explore relationships between sensitivity analysis, the variation of parameters formulae, the fundamental solution and adjoints

Forecasting Industry-Level CPI and PPI Inflation: Does Exchange Rate Pass-Through Matter?

In this paper, we examine whether industry-level forecasts of CPI and PPI inflation can be improved using the ``exchange rate pass-through" effect, that is, when one accounts for the variability of the exchange rate and import prices. An exchange rate depreciation leading to a higher level of pass-through to import prices implies greater expenditure switching, which should be manifested, possibly with a lag, in both producer and consumer prices. We build a forecasting model based on a two or three equation system involving CPI and PPI inflation where the effects of the exchange rate and import prices are taken into account. This setup also incorporates their dynamics, lagged correlations and appropriate restrictions suggested by the theory. We compare the performance of this model with a variety of unrestricted univariate and multivariate time series models, as well as with a model that, in addition, includes standard control variables for inflation, like interest rates and unemployment. Our results indicate that improvements on the forecast accuracy can be effected when one takes into account the possible pass-through effects of exchange rates and import prices on CPI and PPI inflation.Forecasting, Vector Autoregression, Non-linear Models, Inflation, Exchange Rates, Pass-Through Effect

Polytopic Cryptanalysis

Standard differential cryptanalysis uses statistical dependencies between the difference of two plaintexts and the difference of the respective two ciphertexts to attack a cipher. Here we introduce polytopic cryptanalysis which considers interdependencies between larger sets of texts as they traverse through the cipher. We prove that the methodology of standard differential cryptanalysis can unambiguously be extended and transferred to the polytopic case including impossible differentials. We show that impossible polytopic transitions have generic advantages over impossible differentials. To demonstrate the practical relevance of the generalization, we present new low-data attacks on round-reduced DES and AES using impossible polytopic transitions that are able to compete with existing attacks, partially outperforming these

Inhibitory control, impulsivity, and recreational substance use

This thesis explores the involvement of self-control and inhibitory control mechanisms in the early stages of drug use and addiction, and investigates specific psychological processes that are thought to be risk factors for substance use and abuse. An "Intention, Impulse and Control (lIC) framework" is developed, uniting principles drawn from a variety of contemporary perspectives in identifying factors likely to influence whether an individual encounters and engages in substance use. Interrelationships between different self-report and laboratory-based behavioural measures of the psychological constructs implicated by this framework are examined via a cross-sectional study of 497 undergraduate students. Reflecting other findings in the literature, associations between self-report and behavioural measures are found to be weak or non-existent. Factor analysis of the self-report measures yields indices of three key trait constructs: approach tendencies, avoidance tendencies, and cognitive control. The ensuing research programme tests some predictions of the lIC framework, assessing cross-sectional and longitudinal relationships in a large sample of students who use alcohol and other substances recreationally. Cross-sectional analyses probe the differential involvement of various factors including attitudes, recent stress, approach tendencies, avoidance tendencies, and cognitive control. Substance use is found to be strongly associated with attitudes, life stress, and cognitive control, but not with approach or avoidance tendencies. For a subset of 88 participants who were reassessed between one and two years after baseline testing, longitudinal analyses address whether (a) pre-existing impairments of self-control processes predispose some individuals towards substance abuse, and (b) substance use itself leads to diminished self-control. Although methodological limitations mean that caution is needed when interpreting these data, the analyses indicate no causal connections between cognitive control, either at baseline or in terms of change over time, and changes in substance use. The implications of the findings for current theories of addiction, and for future research, are considered

Ground-state phase diagram of the square lattice Hubbard model from density matrix embedding theory

We compute the ground-state phase diagram of the Hubbard and frustrated Hubbard models on the square lattice with density matrix embedding theory using clusters of up to 16 sites. We provide an error model to estimate the reliability of the computations and complexity of the physics at different points in the diagram. We find superconductivity in the ground-state as well as competition between inhomogeneous charge, spin, and pairing states at low doping. The estimated errors in the study are below T$_c$ in the cuprates and on the scale of contributions in real materials that are neglected in the Hubbard model