Showing papers by "National Research University – Higher School of Economics published in 2011"

Software risk management

Abstract: Modern software development faces many challenges nowadays In order to avoiding, minimizing, and monitoring the risks and their impact, it is important to identify, estimate and evaluate the risks The study addresses software risk management in software development area An approach to analysis, structuring, and usage is proposed for the information technology (IT) projects in the risk management context It is based on the study of the existing theoretical knowledge and practices and examples of better management The author provides recommendations on software risk management and gives a brief overview of the automated software tools

Complete set of cut-and-join operators in the Hurwitz-Kontsevich theory

Abstract: We define cut-and-join operators in Hurwitz theory for merging two branch points of an arbitrary type. These operators have two alternative descriptions: (1) the GL characters are their eigenfunctions and the symmetric group characters are their eigenvalues; (2) they can be represented as W-type differential operators (in particular, acting on the time variables in the Hurwitz-Kontsevich τ-function). The operators have the simplest form when expressed in terms of the Miwa variables. They form an important commutative associative algebra, a universal Hurwitz algebra, generalizing all group algebra centers of particular symmetric groups used to describe the universal Hurwitz numbers of particular orders. This algebra expresses arbitrary Hurwitz numbers as values of a distinguished linear form on the linear space of Young diagrams evaluated on the product of all diagrams characterizing particular ramification points of the branched covering.

Super Liouville conformal blocks from N = 2 SU(2) quiver gauge theories

Abstract: The conjecture about the correspondence between instanton partition functions in the N = 2 SUSY Yang-Mills theory and conformal blocks of two-dimensional conformal field theories is extended to the case of the N = 1 supersymmetric conformal blocks. We find that the necessary modification of the moduli space of instantons requires additional restriction of Z (2)-symmetry. This leads to an explicit form of the N =1 superconformal blocks in terms of Young diagrams with two sorts of cells.

PBW FILTRATION AND BASES FOR IRREDUCIBLE MODULES IN TYPE An

Abstract: We study the PBW filtration on the highest weight representations V(λ) of $$ \mathfrak{s}{\mathfrak{l}_{n + 1}} $$ . This filtration is induced by the standard degree filtration on $$ {\text{U}}\left( {{\mathfrak{n}^{-} }} \right) $$ . We give a description of the associated graded $$ S\left( {{\mathfrak{n}^{-} }} \right) $$ -module gr V(λ) in terms of generators and relations. We also construct a basis of gr V(λ). As an application we derive a graded combinatorial character formula for V(λ), and we obtain a new class of bases of the modules V(λ) conjectured by Vinberg in 2005.

On the Fundamental Group of the Complement of a Complex Hyperplane Arrangement

Abstract: We construct two combinatorially equivalent line arrangements in the complex projective plane such that the fundamental groups of their complements are not isomorphic. The proof uses a new invariant of the fundamental group of the complement to a line arrangement of a given combinatorial type with respect to isomorphisms inducing the canonical isomorphism of the first homology groups.

On the makar-limanov, derksen invariants, and finite automorphism groups of algebraic varieties

Abstract: A simple method of constructing a big stock of algebraic varieties with trivial Makar-Limanov invariant is described, the Derksen invariant of some vari- eties is computed, the generalizations of the Makar-Limanov and Derksen invariants are introduced and discussed, and some results on the Jordan property of automor- phism groups of algebraic varieties are obtained

Quantum continuous $\mathfrak{gl}_{\infty}$: Semiinfinite construction of representations

Abstract: We begin a study of the representation theory of quantum continuous gl∞, which we denote by E. This algebra depends on two parameters and is a deformed version of the enveloping algebra of the Lie algebra of difference operators acting on the space of Laurent polynomials in one variable. Fundamental representations of E are labeled by a continuous parameter u∈C. The representation theory of E has many properties familiar from the representation theory of gl∞: vector representations, Fock modules, and semiinfinite constructions of modules. Using tensor products of vector representations, we construct surjective homomorphisms from E to spherical double affine Hecke algebras SHN for all N. A key step in this construction is an identification of a natural basis of the tensor products of vector representations with Macdonald polynomials. We also show that one of the Fock representations is isomorphic to the module constructed earlier by means of the K-theory of Hilbert schemes.

Subnational Appointments in Authoritarian Regimes: Evidence from Russian Gubernatorial Appointments

Abstract: Elections are among the most important and least understood institutions in contemporary authoritarian regimes. Theoretically, electoral authoritarian regimes should have an informational advantage that makes them more robust than other types of authoritarian regimes, but much empirical evidence suggests otherwise. In this paper we offer a new perspective on why this might be the case. Specifically, we consider how authoritarian elections influence a ruler’s choices in making cadre appointments. We argue that the imperative of winning authoritarian elections forces authoritarian leaders to prioritize the appointment of politically loyal cadres, who can help the regime win elections. This choice often comes at the expense of appointing officials who are competent at making good public policy and promoting economic development, factors that may contribute to long-term regime stability. We test this theory using an original dataset of gubernatorial appointments in one leading contemporary authoritarian regime, Russia.

Russian Federation. Health system review.

Abstract: The HiT reviews are country-based reports that provide a detailed description of a health system and of policy initiatives in progress or under development. HiTs examine different approaches to the organization, financing and delivery of health services and the role of the main actors in health systems; describe the institutional framework, process, content and implementation of health and health care policies; and highlight challenges and areas that require more in-depth analysis. At independence from the Soviet Union in 1991, the Russian health system inherited an extensive, centralized Semashko system, but was quick to reform health financing by adopting a mandatory health insurance (MHI) model in 1993. MHI was introduced in order to open up an earmarked stream of funding for health care in the face of severe fiscal constraints. While the health system has evolved and changed significantly since the early 1990 s, the legacy of having been a highly centralized system focused on universal access to basic care remains. High energy prices on world markets have ensured greater macroeconomic stability, a budget surplus and improvements in living standards for most of the Russian population. However, despite an overall reduction in the poverty rate, there is a marked urban rural split and rural populations have worse health and poorer access to health services than urban populations. The increase in budgetary resources available to policy-makers have led to a number of recent federal-level health programmes that have focused on the delivery of services and increasing funding for priority areas including primary care provision in rural areas. Nevertheless, public health spending in the Russian Federation remains relatively low given the resources available. However, it is also clear that, even with the current level of financing, the performance of the health system could be improved. Provider payment mechanisms are the main obstacle to improving technical efficiency in the Russian health system, as most budget funding channelled through local government is input based. For this reason, the most recent reforms as well as legislation in the pipeline seek to ensure all health care funding is channelled through a strengthened MHI system with contracts for provider payments being made using output-based measures.

Base change for semiorthogonal decompositions

Abstract: Let X be an algebraic variety over a base scheme S and :T!S a base change. Given an admissible subcategoryA inD b (X), the bounded derived category of coherent sheaves on X, we construct under some technical conditions an admissible subcategory AT inD b (X S T ), called the base change ofA, in such a way that the following base change theorem holds: if a semiorthogonal decomposition ofD b (X) is given, then the base changes of its components form a semiorthogonal decomposition ofD b (X S T ). As an intermediate step, we construct a compatible system of semiorthogonal decompositions of the unbounded derived category of quasicoherent sheaves onX and of the category of perfect complexes on X. As an application, we prove that the projection functors of a semiorthogonal decomposition are kernel functors.

Three Approaches to Estimate Latent Interaction Effects: Intention and Perceived Behavioral Control in the Theory of Planned Behavior

Abstract: Interaction effects between explanatory constructs are an important part of many social theories. Analyses of interaction effects between variables using regression techniques have low power because they do not control for measurement errors. Therefore, latent interaction modeling using structural equation modeling (SEM) has been proposed as a better alternative to test for interaction effects. In contrast to traditional and complicated ‘constrained’ SEM approaches, two recent developments, the unconstrained approach and the residual centering approach, are especially attractive for applied researchers as they are much easier to implement. However, applied researchers still seem to be unsure about how to apply these approaches. In this study, we illustrate the use of the unconstrained and the residual centering approach and compare these approaches with the constrained approach of Algina and Moulder (2001) using data from a field study of 1,442 students. Theoretical background is the theory of planned behavior (Ajzen, 1991) in which we test the proposed interaction between an individual’s intention to perform a behavior and perceived behavioral control (PBC) on behavior. The illustration should assist researchers interested in testing interaction effects using structural equation modeling.

Equivariant K-theory of Hilbert schemes via shuffle algebra

Abstract: In this paper we construct the action of Ding-Iohara and shuffle algebras on the sum of localized equivariant K-groups of Hilbert schemes of points on C2. We show that commutative elements Ki of shuffle algebra act through vertex operators over the positive part {hi}i>0 of the Heisenberg algebra in these K-groups. Hence we get an action of Heisenberg algebra itself. Finally, we normalize the basis of the structure sheaves of fixed points in such a way that it corresponds to the basis of Macdonald polynomials in the Fock space C[h1,h2,…].

Revisiting numerical pattern mining with formal concept analysis

Abstract: We investigate the problem of mining numerical data with Formal Concept Analysis. The usual way is to use a scaling procedure -transforming numerical attributes into binary ones- leading either to a loss of information or of efficiency, in particular w.r.t. the volume of extracted patterns. By contrast, we propose to directlywork on numerical data in a more precise and efficient way. For that, the notions of closed patterns, generators and equivalent classes are revisited in the numerical context. Moreover, two algorithms are proposed and tested in an evaluation involving real-world data, showing the quality of the present approach.

Instanton moduli spaces and bases in coset conformal field theory

Abstract: Recently proposed relation between conformal field theories in two dimensions and supersymmetric gauge theories in four dimensions predicts the existence of the distinguished basis in the space of local fields in CFT. This basis has a number of remarkable properties, one of them is the complete factorization of the coefficients of the operator product expansion. We consider a particular case of the U(r) gauge theory on C^2/Z_p which corresponds to a certain coset conformal field theory and describe the properties of this basis. We argue that in the case p=2, r=2 there exist different bases. We give an explicit construction of one of them. For another basis we propose the formula for matrix elements.

Quantum continuous $\mathfrak{gl}_{\infty}$: Tensor products of Fock modules and $\mathcal{W}_{n}$-characters

Abstract: We construct a family of irreducible representations of the quantum continuous gl∞ whose characters coincide with the characters of representations in the minimal models of the Wn-algebras of gln type. In particular, we obtain a simple combinatorial model for all representations of the Wn-algebras appearing in the minimal models in terms of n interrelating partitions.

Choosing the number of clusters

Abstract: The issue of determining ‘the right number of clusters’ is attracting ever growing interest. The paper reviews published work on the issue with respect to mixture of distributions, partition, especially in k-means clustering, and hierarchical cluster structures. Some perspective directions for further developments are outlined.

Yangians and cohomology rings of Laumon spaces

Abstract: Laumon moduli spaces are certain smooth closures of the moduli spaces of maps from the projective line to the flag variety of GL n. We construct the action of the Yangian of sln in the cohomology of Laumon spaces by certain natural correspon- dences. We construct the action of the affine Yangian (two-parametric deformation of the universal enveloping algebra of the universal central extension of sln(s ±1 , t)) in the cohomology of the affine version of Laumon spaces. We compute the matrix coefficients of the generators of the affine Yangian in the fixed point basis of coho- mology. This basis is an affine analog of the Gelfand-Tsetlin basis. The affine analog of the Gelfand-Tsetlin algebra surjects onto the equivariant cohomology rings of the affine Laumon spaces. The cohomology ring of the moduli space Mn,d of torsion free sheaves on the plane, of rank n and second Chern class d, trivialized at infinity, is

Global Oil Risks in the Early 21st Century

Abstract: The Deepwater Horizon incident demonstrated that most of the oil left is deep offshore or in other difficult to reach locations. Moreover, obtaining the oil remaining in currently producing reservoirs requires additional equipment and technology that comes at a higher price in both capital and energy. In this regard, the physical limitations on producing ever-increasing quantities of oil are highlighted as well as the possibility of the peak of production occurring this decade. The economics of oil supply and demand are also briefly discussed showing why the available supply is basically fixed in the short to medium term. Also, an alarm bell for economic recessions is shown to be when energy takes a disproportionate amount of total consumer expenditures. In this context, risk mitigation practices in government and business are called for. As for the former, early education of the citizenry of the risk of economic contraction is a prudent policy to minimize potential future social discord. As for the latter, all business operations should be examined with the aim of building in resilience and preparing for a scenario in which capital and energy are much more expensive than in the business-as-usual one.

A Finite Analog of the AGT Relation I: Finite W -Algebras and Quasimaps’ Spaces

Abstract: Recently Alday, Gaiotto and Tachikawa [2] proposed a conjecture relating 4-dimensional super-symmetric gauge theory for a gauge group G with certain 2-dimensional conformal field theory. This conjecture implies the existence of certain structures on the (equivariant) intersection cohomology of the Uhlenbeck partial compactification of the moduli space of framed G-bundles on \({\mathbb{P}^2}\) . More precisely, it predicts the existence of an action of the corresponding W-algebra on the above cohomology, satisfying certain properties.

Oligopolistic markets with sequential search and production cost uncertainty

Abstract: This article analyzes a sequential search model where firms face identical but stochastic production costs, the realizations of which are unknown to consumers. We characterize a perfect Bayesian equilibrium satisfying a reservation price property and provide a sufficient condition for such an equilibrium to exist. We show that (i) firms set on average higher prices and make larger profits compared to the scenario where consumers observe production costs, (ii) expected prices and consumer welfare can be non-monotonic in the number of firms, and (iii) the impact of production cost uncertainty vanishes as the number of firms becomes very large.

Degenerate flag varieties and the median Genocchi numbers

Abstract: We study the $\bG_a^M$ degenerations $\Fl^a_\la$ of the type $A$ flag varieties $\Fl_\la$. We describe these degenerations explicitly as subvarieties in the products of Grassmanians. We construct cell decompositions of $\Fl^a_\la$ and show that for complete flags the number of cells is equal to the normalized median Genocchi numbers $h_n$. This leads to a new combinatorial definition of the numbers $h_n$. We also compute the Poincar\' e polynomials of the complete degenerate flag varieties via a natural statistics on the set of Dellac's configurations, similar to the length statistics on the set of permutations. We thus obtain a natural $q$-version of the normalized median Genocchi numbers.

PBW Filtration and Bases for Symplectic Lie Algebras

Abstract: We study the PBW filtration on the highest weight representations $V(\la)$ of $\msp_{2n}$. This filtration is induced by the standard degree filtration on $U( ^-)$. We give a description of the associated graded $S( ^-)$-module $gr V(\la)$ in terms of generators and relations. We also construct a basis of $gr V(\la)$. As an application we derive a graded combinatorial formula for the character of $V(\la)$ and obtain a new class of bases of the modules $V(\la)$.

Health Equity and Financial Protection: Streamlined Analysis with ADePT Software

Abstract: This book provides a step-by-step guide to the use of ADePT for the quantitative analysis of equity and financial protection in the health sector. It also elucidates the concepts and methods used by the software and supplies more detailed, technical explanations. The book is geared to practitioners, researchers, students, and teachers who have some knowledge of quantitative techniques and the manipulation of household data using such programs as SPSS or Stata.