1,721,023 research outputs found
Quantum immanants, double Young-Capelli bitableaux and Schur shifted symmetric functions
Get PDFWe propose a new method for a unified study of some of the main features of the theory of the center
of the enveloping algebra U(gl(n)) and of the algebra of shifted symmetric polynomials, that allows the whole theory to be developed, in a transparent and concise way, from the representation-theoretic point of view, that is entirely in the center of U(gl(n)).
Our methodological innovation is the systematic use of the superalgebraic method of virtual variables for gl(n), which is, in turn,
an extension of Capelli's method of ``variabili ausiliarie''.
The passage for the
algebras and
is here obtained both as direct and inverse limit in the category of filtered algebras.
The present approach leads to proofs that are almost direct consequences of the definitions and
constructions: they often reduce to a few lines computation
Exact results for topological strings on resolved Y**p,q singularities
No full textWe obtain exact results in \alpha' for open and closed A-model topological string amplitudes on a large class of toric Calabi-Yau threefolds by using their correspondence with five dimensional gauge theories. The toric Calabi-Yau's that we analyze are obtained as minimal resolution of cones over Y(p,q) manifolds and give rise via M-theory compactification to SU(p) gauge theories on R^4 x S^1. As an application we present a detailed study of the local F_2 case and compute open and closed genus zero Gromov-Witten invariants of the C^3/Z_4 orbifold. We also display the modular structure of the topological wave function and give predictions for higher genus amplitudes.The mirror curve in this case is the spectral curve of the relativistic A_1 Toda chain. Our results also indicate the existence of a wider class of relativistic integrable systems associated to generic Y(p,q) geometries
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Deep Reinforcement Trading with Predictable Returns
Get PDFClassical portfolio optimization often requires forecasting asset returns and
their corresponding variances in spite of the low signal-to-noise ratio
provided in the financial markets. Modern deep reinforcement learning (DRL)
offers a framework for optimizing sequential trader decisions but lacks
theoretical guarantees of convergence. On the other hand, the performances on
real financial trading problems are strongly affected by the goodness of the
signal used to predict returns. To disentangle the effects coming from return
unpredictability from those coming from algorithm un-trainability, we
investigate the performance of model-free DRL traders in a market environment
with different known mean-reverting factors driving the dynamics. When the
framework admits an exact dynamic programming solution, we can assess the
limits and capabilities of different value-based algorithms to retrieve
meaningful trading signals in a data-driven manner. We consider DRL agents that
leverage classical strategies to increase their performances and we show that
this approach guarantees flexibility, outperforming the benchmark strategy when
the price dynamics is misspecified and some original assumptions on the market
environment are violated with the presence of extreme events and volatility
clustering.Comment: 37 pages, 15 figures. Added a more detailed appendix explaining the
approached followed. Revised version to be published in Physyca
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Reinforcement Learning Policy Recommendation for Interbank Network Stability
Get PDFIn this paper, we analyze the effect of a policy recommendation on the
performance of an artificial interbank market. Financial institutions stipulate
lending agreements following a public recommendation and their individual
information. The former is modeled by a reinforcement learning optimal policy
that maximizes the system's fitness and gathers information on the economic
environment. The policy recommendation directs economic actors to create credit
relationships through the optimal choice between a low interest rate or a high
liquidity supply. The latter, based on the agents' balance sheet, allows
determining the liquidity supply and interest rate that the banks optimally
offer their clients within the market. Thanks to the combination between the
public and the private signal, financial institutions create or cut their
credit connections over time via a preferential attachment evolving procedure
able to generate a dynamic network. Our results show that the emergence of a
core-periphery interbank network, combined with a certain level of homogeneity
in the size of lenders and borrowers, is essential to ensure the system's
resilience. Moreover, the optimal policy recommendation obtained through
reinforcement learning is crucial in mitigating systemic risk.Comment: 63 pages, 24 figures. Submitted the revised version that is going to
be published on the Journal of Financial Stabilit
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