• A
• A
• A
• ABC
• ABC
• ABC
• А
• А
• А
• А
• А
Regular version of the site
Of all publications in the section: 3 817
Sort:
by name
by year
Working paper
Prokhorov Y., Duncan A., Cheltsov I. et al. math. arxive. Cornell University, 2019
We study the complexity of birational self-maps of a projective threefold X by looking at the birational type of surfaces contracted. These surfaces are birational to the product of the projective line with a smooth projective curve. We prove that the genus of the curves occuring is unbounded if and only if X is birational to a conic bundle or a fibration into cubic surfaces. Similarly, we prove that the gonality of the curves is unbounded if and only if X is birational to a conic bundle.
Working paper
Vladimir L. Popov. arxiv.org. math. Cornell University, 2015. No. 1502.02167.
According to the classical theorem, every irreducible algebraic variety endowed with a nontrivial rational action of a connected linear algebraic group is birationally isomorphic to a product of another algebraic variety and the s-dimensional projectice space with positive s. We show that the classical proof of this theorem actually works only in characteristic 0 and we give a characteristic free proof of it. To this end we prove and use a characterization of connected linear algebraic groups G with the property that every rational action of G on an irreducible algebraic variety is birationally equivalent to a regular action of G on an affine algebraic variety.
Working paper
Schnittke E. Linguistics. WP BRP. НИУ ВШЭ, 2014. No. 9.
Working paper
Sakevich Victoria I., Denisov B. P. Sociology. SOC. Высшая школа экономики, 2014. No. WP BRP 42/SOC/2014.
The paper considers the changes in major proximate determinants of fertility in Russia within the framework of demographic transition theory and Bongaarts approach to fertility analysis. After World War II Russian fertility became fully controlled process. The complex interplay of abortion and contraception during the Soviet period resulted in a very high abortion level. Russian government has almost never supported and promoted family planning as alternative to abortion. However couple's preferences of small offspring appeared more powerful than the will of authorities. Current trends show that albeit lack of governmental support the society itself is evolving towards more humanistic and effective birth control. Estimates made upon recent surveys' data confirm the validity of official statistics and thus the reality of favorable trend of abortion decline.
Working paper
Podkolzina E., Voytova T. I. Public Administration. PA. Высшая школа экономики, 2011. No. 01.
The main goal of public procurement reform in Russia, initiated in 2005, was to prevent corrupt deals between suppliers and procurers. That is why the public procurement law favors formal mechanisms to govern most of the stages of procurement: the procurer is not allowed to take into account the reputation of the supplier when he announces calls for bids and selects the supplier, and he is prescribed to use the legal system (courts) if he is not satisfied with the contract performance. Since the efficiency of formal institutions is not very high, these mechanisms are complemented by a “formalized informal instrument” - blacklisting opportunistic suppliers, which is believed to substitute for reputation mechanisms when formal mechanisms are weak. In this paper, we show how and why the institutional environment in Russia makes the blacklisting of opportunistic suppliers irrelevant. We explore how the percentage of contract breaches out of the total number of signed contracts is related to corruption and transparency measures for Russian regions. We also argue that such factors as measurement costs, verification costs, length of contracts and lawsuit amounts influence the probability of winning a legal action for a contract breach.
Working paper
Muravyev Alexander. IZA Discussion Paper. IZA, 2016. No. 10436.
This paper provides new evidence on the structure, dynamics and performance effects of corporate boards in publicly traded companies in Russia. It takes advantage of a new and unique longitudinal dataset of virtually all Russian companies whose shares were traded in the RTS/MICEX/MOEX over 1998-2014. The analysis highlights a number of strong trends in the evolution of boards of directors, such as the declining participation of insider directors and the increasing participation of foreign and female directors. It also shows that board characteristics are linked to company performance (the market-to-book ratio, Tobin’s Q, ROE and ROA), suggesting that boards of directors play a non-trivial role in corporate governance in Russia. Testing for structural breaks in the relationship between board composition and firm performance provides some evidence of the changing role of corporate boards over time.
Working paper
Kaledin D. B. arxiv.org. math. Cornell University, 2015
We give a simple construction of the correspondence between square-zero extensions R′ of a ring R by an R-bimodule M and second MacLane cohomology classes of R with coefficients in M (the simplest non-trivial case of the construction is R=M=Z/p, R′=Z/p2, thus the Bokstein homomorphism of the title). Following Jibladze and Pirashvili, we treat MacLane cohomology as cohomology of non-additive endofunctors of the category of projective R-modules. We explain how to describe liftings of R-modules and complexes of R-modules to R′ in terms of data purely over R. We show that if R is commutative, then commutative square-zero extensions R′ correspond to multiplicative extensions of endofunctors. We then explore in detail one particular multiplicative non-additive endofunctor constructed from cyclic powers of a module V over a commutative ring R annihilated by a prime p. In this case, R′ is the second Witt vectors ring W2(R) considered as a square-zero extension of R by the Frobenius twist R(1).
Working paper
Kudryashov Y. arxiv.org. math. Cornell University, 2012
In this article, we extend the phenomena of a bony attractor from a rather artificial class of step skew products to the class of diffeomorphisms on the Cartesian product of the two-dimensional torus by a sphere of arbitrary dimension.
Working paper
Lazareva O. Economics. EC. Высшая школа экономики, 2012. No. 21.

This paper estimates the effect of economic shocks that affect families with young children on children’s health, educational and behavioral outcomes in adolescence.  Transition period in Russia provides a natural experiment setting for estimating this effect.  During the economic turmoil of early transition many people lost their jobs, experienced salary declines or occupational downgrading. These individual labor market shocks were mainly caused by the structural changes in the economy. Analyzing household survey data from Russia I find that children who were under the age of five and whose parents were negatively affected during the early transition have poorer health in adolescence and are less likely to have completed high school. For the comparison group  –  children who were at the school age during the early transition  –  there is an effect on educational outcomes and risky behaviors but not on health. Absence of a father in a family during the early transition years has a negative health effect only for the younger age group. I also find differential effects for boys and girls, by mother and father.

Working paper
Shramov K., Prokhorov Y. math. arxive. Cornell University, 2019
We classify compact complex surfaces whose groups of bimeromorphic selfmaps have bounded finite subgroups. We also prove that the stabilizer of a point in the automorphism group of a compact complex surface of zero Kodaira dimension, as well as the stabilizer of a point in the automorphism group of an arbitrary compact Kaehler manifold of non-negative Kodaira dimension, always has bounded finite subgroups.
Working paper
Goncharuk N. B., Kudryashov Y. arxiv.org. math. Cornell University, 2015. No. 1504.03313.
In this article we prove in a new way that a generic polynomial vector field in ℂ² possesses countably many homologically independent limit cycles. The new proof needs no estimates on integrals, provides thinner exceptional set for quadratic vector fields, and provides limit cycles that stay in a bounded domain.
Working paper
Andreev N. A. Financial Economics. FE. Высшая школа экономики, 2017. No. WP BRP 59/FE/2017.
We study the boundedness properties of the value function for a general worst-case scenario stochastic dynamic programming problem. For the portfolio selection problem,we present sufficient economically reasonable conditions for the finitness and uniform boundedness of the value function. The results can be used to decide if the problem is ill-posed and to correctly solve the Bellman-Isaacs equation with an appropriate numeric scheme.
Working paper
Loginov K., Birkar C. math. arxive. Cornell University, 2020
In this paper we investigate non-rationality of divisors on 3-fold log Fano fibrations (X,B)→Z under mild conditions. We show that if D is a component of B with coefficient ≥t>0 which is contracted to a point on Z, then D is birational to ℙ^1×C where C is a smooth projective curve with gonality bounded depending only on t. Moreover, if t>1/2, then genus of C is bounded depending only on t.
Working paper
Kurnosov N. arxiv.org. math. Cornell University, 2015
We prove that b2 is bounded for hyperk¨ahler manifolds with vanishing odd-Betti numbers. The explicit upper boundary is conjectured. Following the method described by Sawon we prove that b2 is bounded in dimension eight and ten in the case of vanishing odd-Betti numbers by 24 and 25 respectively.
Working paper
Ovchinnikov A., Pogudin G., Vo T. Working papers by Cornell University. Cornell University, 2018
Elimination of unknowns in systems of equations, starting with Gaussian elimination, is a problem of general interest. The problem of finding an a priori upper bound for the number of differentiations in elimination of unknowns in a system of differential-algebraic equations (DAEs) is an important challenge, going back to Ritt (1932). The first characterization of this via an asymptotic analysis is due to Grigoriev's result (1989) on quantifier elimination in differential fields, but the challenge still remained. In this paper, we present a new bound, which is a major improvement over the previously known results. We also present a new lower bound, which shows asymptotic tightness of our upper bound in low dimensions, which are frequently occurring in applications. Finally, we discuss applications of our results to designing new algorithms for elimination of unknowns in systems of DAEs.
Working paper
Przyjalkowski V., Shramov K. math. arxive. Cornell University, 2016
We prove that if a smooth variety with non-positive canonical class can be embedded into a weighted projective space of dimension~n as a well formed complete intersection and it is not an intersection with a linear cone therein, then the weights of the weighted projective space do not exceed n+1. Based on this bound we classify all smooth Fano complete intersections of dimensions 4 and 5, and compute their invariants.
Working paper
Penskoi A., Nadirashvili N. S., Berdnikov A. S. math. arxive. Cornell University, 2016
The known upper bounds for the multiplicities of the Laplace-Beltrami operator eigenvalues on the real projective plane are improved for the eigenvalues with even indexes. Upper bounds for Dirichlet, Neumann and Steklov eigenvalues on the real projective plane with holes are also provided.
Working paper
Feigin B. L., Miwa T., Jimbo M. et al. Cornell University Library, 2013. No. 1309.2147.
We construct an analog of the subalgebra $U\mathfrak{gl}(n)\otimes U\mathfrak{gl}(m)\subset U\mathfrak{gl}(m+n)$ in the setting of quantum toroidal algebras and study the restrictions of various representations to this subalgebra.