We develop a simple partial-equilibrium model of endogenous city structure formation. No production externalities are at work, the only two forces shaping the spatial configurations of the city being love for variety (on the consumer side) and seeking for a better access to the market (on the firm side). We show that, unlike in existing models of a similar nature, our model generates clustering rather than co-agglomeration. Namely, if there are few firms relative to the urban population size, then firms tend to cluster at the city center, while consumers choose to reside on the outskirts. Otherwise, the opposite holds. Although a continuum of equilibrium city structures may emerge, we show that all spatial equilibria are segregated. In addition, the market outcome features spatial price dispersion, even though our framework does not involve imperfect information and search costs on the consumer side.

In this paper the relation between the cluster integrable systems and q-difference equations is extended beyond the Painlevé case. We consider the class of hyperelliptic curves when the Newton polygons contain only four boundary points. The corresponding cluster integrable Toda systems are presented, and their discrete automorphisms are identified with certain reductions of the Hirota difference equation. We also construct non-autonomous versions of these equations and find, that their solutions are expressed in terms of 5d Nekrasov functions with the Chern-Simons contributions, while in the autonomous case these equations are solved in terms of the Riemann theta-functions.

We construct two small resolutions of singularities of the Coble fourfold (the double cover of the four-dimensional projective space branched over the Igusa quartic). We use them to show that all S_6-invariant three-dimensional quartics are birational to conic bundles over the quintic del Pezzo surface with the discriminant curves from the Wiman-Edge pencil. As an application, we check that S_6-invariant three-dimensional quartics are unirational, obtain new proofs of rationality of four special quartics among them and irrationality of the others, and describe their Weil divisor class groups as S_6-representations.

The paper proposes a linguistic approach to studying code-switching IT discourse of Moscovian IT specialists. The topic is of special interest since nowadays code-switching dominates in a number of professional spheres such as informational technologies, marketing and telecommunications. It also becomes a new language for the modern generation and moreover, a necessary tool for establishing contacts and demonstrating community affiliation. This new code exists not only within workplaces but also beyond them, that is why the aim is to provide a thorough linguistic and functional description on this topic. Also, there is an in-depth research into how IT discourse shapes Russian digital language on the whole. The methodology used for research is the Matrix Language Frame Model by C.Myers-Scotton (1993). The language units, which are represented by code-switches, are also analyzed in terms of their syntactic, morphological features and pragmatic functions.

Political attitudes and positions may tend to change in critical and unstable times, especially for young minds. Social environment of individuals, mostly presented by their social networks, has significant impact on their evaluations. The relationship between political views and social affiliations is difficult to analyze: do people influence each other’s opinions so that they shift over time, or do their political attitudes act as a ground for attraction of individuals to each other and social network construction? In this research, we use longitudinal attitudinal and network data on a sample of one hundred first-year students, analyzed with social network analysis methods and structural-equation modeling. We found tendencies to conformity and shifting individuals’ positions toward the political views of their peers, formed by friendship, rather than by study task ties. Also, political attitudes are appeared to be a driver of relationships formation. 

The paper gives the author’s view on the cognitive political discourse analysis procedure by researching the case of teaching creative translation. Of a particular interest is the fact that the research material is based on the example of the discourse analysis of modern political terminology and other non-equivalent vocabulary within the bounds of political contexts. Unlike traditional approaches connecting creativity to literary texts studies, the paper deals with the methodology of comprehending and translating foreign academic and scientific texts. Cognitive study of the aspects of contextual actualization of political concepts in the English and Russian discourses by means of comparative analysis is aimed at professional explanation of motivation in choosing translation equivalents. The algorithm of making up an associative thesaurus based on cognitive signs of lexical marking has been used as the major tool of political discourse analysis as well as the foundation for the original creative model of teaching translation suggested by the author.

We examine how idea exposure produces cognitive stimulation. Study participants were given stimulus ideas with a low or high level of originality, or with absurd content.  Stimuli were exposed in conditions of face-to-face communication and with computer and paper mediation, respectively. Three parameters of creativity were analyzed: Fluency, flexibility, and originality. Results revealed a positive effect on fluency scores for face-to-face communication. This effect is the most evident for the exposure of absurd stimulus ideas. We also found a positive effect on originality scores for highly original stimulus ideas.

Coherence is a semantic property of the text to make sense to readers or listeners and is crucial for any text. Various coherence measures have been developed for assessment of discourse abilities in different clinical populations. However, the results of decades of research on coherence of speech of individuals with brain damage have yielded contradictive results. We suggest that this might be due to the different sensitivity of the methods. In this study we two measures of global coherence and five measures of local coherence on the same set of texts by healthy speakers of Russian and people with dynamic aphasia in order to find which methods allow to distinguish between the two groups and how these results correlate. The material for the study is texts from the Russian CliPS corpus which is a collection of oral retellings of the pear film by individuals with brain damage and healthy speakers of Russian language.

In this article we prove that quasi-free algebra over noetherian ring is coherent. In particular, we get that the category of left finite-presented modules over this algebra is abelian.

We define the triangulated category of relative singularities of a closed subscheme in a scheme. When the closed subscheme is a Cartier divisor, we consider matrix factorizations of the related section of a line bundle, and their analogues with locally free sheaves replaced by coherent ones. The appropriate exotic derived category of coherent matrix factorizations is then identified with the triangulated category of relative singularities, while the similar exotic derived category of locally free matrix factorizations is its full subcategory. The latter category is identified with the kernel of the direct image functor corresponding to the closed embedding of the zero locus and acting between the conventional (absolute) triangulated categories of singularities. Similar results are obtained for matrix factorizations of infinite rank; and two different "large" versions of the triangulated category of relative singularities, corresponding to the approaches of Orlov and Krause, are identified in the case of a Cartier divisor. Contravariant (coherent) and covariant (quasi-coherent) versions of the Serre-Grothendieck duality theorems for matrix factorizations are established, and pull-backs and push-forwards of matrix factorizations are discussed at length. A number of general results about derived categories of the second kind for CDG-modules over quasi-coherent CDG-algebras are proven on the way. Hochschild (co)homology of matrix factorization categories are discussed in an appendix written in collaboration with A.I. Efimov.

The convolution ring K^{GL_n(\OOO)⋊ℂ×}(Gr_{GL_n}) was identified with a quantum unipotent cell of the loop group LSL_2 in [Cautis-Williams, arXiv:1801.08111]. We identify the basis formed by the classes of irreducible equivariant perverse coherent sheaves with the dual canonical basis of the quantum unipotent cell.

A Hermitian symplectic manifold is a complex manifold endowed with a symplectic form ω, for which the bilinear form ω(I·, ·) is positive definite. In this work we prove ddc -lemma for 1- and (1,1)-forms for compact Hermitian symplectic manifolds of dimension 3. This shows that Albanese map for such manifolds is well-defined and allows one to prove Kahlerness if the dimension of the Albanese image of a manifold is maximal.

Efficient regulation of internal homeostasis and defending it against perturbations requires complex behavioral strategies. However, the computational principles mediating brain’s homeostatic regulation of reward and associative learning remain undefined. Here we use a definition of primary rewards, as outcomes fulfilling physiological needs, to build a normative theory showing how learning motivated behavior is modulated by the internal state of the animal. The theory proves that seeking rewards is equivalent to the fundamental objective of physiological stability, defining the notion of physiological rationality of behavior. We further give a formal basis for temporal discounting of reward. It also explains how animals learn to act predictively to preclude prospective homeostatic challenges, and attributes a normative computational role to the modulation of midbrain dopaminergic activity by hypothalamic signals.  

Efficient regulation of internal homeostasis and defending it against perturbations requires complex behavioral strategies. However, the computational principles mediating brain's homeostatic regulation of reward and associative learning remain undefined. Here we use a definition of primary rewards, as outcomes fulfilling physiological needs, to build a normative theory showing how learning motivated behavior is modulated by the internal state of the animal. The theory proves that seeking rewards is equivalent to the fundamental objective of physiological stability, defining the notion of physiological rationality of behavior. We further give a formal basis for temporal discounting of reward. It also explains how animals learn to act predictively to preclude prospective homeostatic challenges, and attributes a normative computational role to the modulation of midbrain dopaminergic activity by hypothalamic signals. 

Let M be a hyperk\"ahler manifold with b2(M)≥5. We improve our earlier results on the Morrison-Kawamata cone conjecture by showing that the Beauville-Bogomolov square of the primitive MBM classes (i.e. the classes whose orthogonal hyperplanes bound the K\"ahler cone in the positive cone, or, in other words, the classes of negative extremal rational curves on deformations of M) is bounded in absolute value by a number depending only on the deformation class of M. The proof uses ergodic theory on homogeneous spaces.

What role can collective action by foreign investors play in an environment characterized by incomplete institutions? We study this question by looking on foreign business associations in the Russian Federation. By interviewing 17 foreign business associations and conducting an online survey of their member firms, we find that business associations play an important welfare-enhancing role in providing a series of support and informational services. However, they do not play a significant role in lobbying the collective interests of their member firms, especially in the current political context in Russia where since the start of the Ukraine crisis the business community seems to have suffered a general loss of influence on political decision making

To what extent does the degree of authoritarian political support depend on collective memories of a past experience with democracy? And how costly is it for a dictator to manipulate such memories with the help of propaganda? In this paper, we develop a political economy model with endogenous reference points, where a dictator strategically recalls traumatic collective memories of past political instability with the help of propaganda, to convince the population that an autocratic status quo is superior to a potential democratic alternative. In our model, both the optimal level of propaganda and collective memories are jointly determined. We show how the marginal benefit of propaganda is positively correlated both with the amount of rent distribution within the elite, and the intensity of a past traumatic experience with democracy. We illustrate our theoretical findings with case-studies of two authoritarian regimes that were preceded by periods of political instability -- the Russian Federation under Vladimir Putin, and Chile under Augusto Pinochet. We then also provide cross-country empirical evidence in support of our argument.

A common feature of the Hungarian, Irish, Spanish and Turkish higher education admission systems is that the students apply for programmes and they are ranked according  to their scores. Students who apply for a programme with the same score are in a tie. Ties  are broken by lottery in Ireland, by objective factors in Turkey (such as date of birth) and  other precisely defined rules in Spain. In Hungary, however, an equal treatment policy is  used, students applying for a programme with the same score are all accepted or rejected  together. In such a situation there is only one question to decide, whether or not to admit  the last group of applicants with the same score who are at the boundary of the quota. Both  concepts can be described in terms of stable score-limits. The strict rejection of the last  group with whom a quota would be violated corresponds to the concept of H-stable (i.e.  higher-stable) score-limits that is currently used in Hungary. We call the other solutions  based on the less strict admission policy as L-stable (i.e. lower-stable) score-limits. We show  that the natural extensions of the Gale-Shapley algorithms produce stable score-limits,  moreover, the applicant-oriented versions result in the lowest score-limits (thus optimal for  students) and the college-oriented versions result in the highest score-limits with regard to  each concept. When comparing the applicant-optimal H-stable and L-stable score-limits we prove that the former limits are always higher for every college. Furthermore, these two  solutions provide upper and lower bounds for any solution arising from a tie-breaking  strategy. Finally we show that both the H-stable and the L-stable applicant-proposing scorelimit algorithms are manipulable.

Let $\Psi$ be the projectivization (i.e., the set of one-dimensional vector subspaces) of a vector space of dimension $\ge 3$ over a field. Let $H$ be a closed (in the pointwise convergence topology) subgroup of the permutation group $\mathfrak{S}_{\Psi}$ of the set $\Psi$. Suppose that $H$ contains the projective group and an arbitrary self-bijection of $\Psi$ transforming a triple of collinear points to a non-collinear triple. It is well-known from \cite{KantorMcDonough} that if $\Psi$ is finite then $H$ contains the alternating subgroup $\mathfrak{A}_{\Psi}$ of $\mathfrak{S}_{\Psi}$. We show in Theorem \ref{density} below that $H=\mathfrak{S}_{\Psi}$, if $\Psi$ is infinite.

Corruption, i.e. regular abuse of public office for private gains, draws substantial attention of researchers in many disciplines. Our paper adds to the experimental literature on corruption a novel experiment on corruption-at-the-top among the real Russian police officers of senior middle rank as experimental subjects (apparently the first study of that kind), which is contrasted to that of ordinary citizens (students in economics). Our experimental design explicitly takes account of the peculiarities of the Russian case during police reform, as well as social and institutional constraints facing anticorruption policies. We find that taking bribes, and especially defending against possible checks of corruption, is quite common to Russian police officers, yet even more typical is their readiness to contribute towards the decrease of the likelihood of this anti-corruption check, even if this contribution leads to private losses. Another typical feature is increased volatility of the frequency and scale of bribery among the police officers (as contrasted to ordinary citizens) when measures aimed at fighting corruption are introduced. We discuss robustness of these findings, as well as their implications for anti-corruption policy.