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Ivan Cherednik

Publications and source records attributed to Ivan Cherednik.

At least 37 records · Page 2Linked to original sources
arXiv2014

On Galois action in rigid DAHA modules

Given an elliptic curve over a field $K$ of algebraic numbers, we associate with it an action of the absolute Galois group $G_K$ in the type $A_1$ rigid DAHA-modules at roots of unity $q$ and over the rings $Z[q^{1/4}]/(p^m)$ for sufficiently general prime $p$. We describe rigid modules in characteristic zero and for such rings. The main examples of rigid modules are generalized nonsymmetric Verlinde algebras; their deformations for arbitrary $q$ are constructed in this paper, which is of independent interest on its own. The Galois action preserves the images of the elliptic braid group in the groups of automorphisms of rigid modules over $Z[q^{1/4}]/(p^m)$. If they are finite in characteristic zero, then $G_K$ acts there and no reduction modulo $(p^m)$ is needed; we find all such cases. In the case of $3$-dimensional DAHA-modules, these images are quotients of equilateral triangle groups directly related to the Livné groups. Also, this paper can be viewed as an extension of the DAHA theory of refined Jones polynomials of torus knots (for $A_1$) to $G_K$.

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arXiv2013

Extremal part of the PBW-filtration and E-polynomials

Given a reduced irreducible root system, the corresponding nil-DAHA is used to calculate the extremal coefficients of nonsymmetric Macdonald polynomials, also called E-polynomails, in the limit t=infinity and for antidominant weights, which is an important ingredient of the new theory of nonsymmetric q-Whittaker function. These coefficients are pure q-powers and their degrees are expected to coincide in the untwisted setting with the extremal degrees of the so-called PBW-filtration in the corresponding finite-dimensional irreducible representations of the simple Lie algebra for any root systems. This is a particular case of a general conjecture in terms of the level-one Demazure modules. We prove this coincidence for all Lie algebras of classical type and for G_2, and also establish the relations of our extremal degrees to minimal q-degrees of the extremal terms of the Kostant q-partition function; they coincide with the latter only for some root systems.

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arXiv2013

Nonsymmetric difference Whittaker functions

Starting with nonsymmetric global difference spherical functions, we define and calculate spinor (nonsymmetric) global q-Whittaker functions for arbitrary reduced root systems, which are reproducing kernels of the DAHA-Fourier transforms of Nil-DAHA and solutions of the q-Toda-Dunkl eigenvalue problem. We introduce the spinor q-Toda-Dunkl operators as limits of the difference Dunkl operators in DAHA theory under the spinor variant of the Ruijsenaars procedure. Their general algebraic theory (any reduced root systems) is the key part of this paper, based on the new technique of W-spinors and corresponding developments in combinatorics of affine root systems.

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arXiv2012

A new take on spherical, Whittaker and Bessel functions (Spherical and Whittaker functions via DAHA I,II)

This paper is based on the lectures given by the first author at Harvard in February and March, 2009. It begins with an introduction to the classical p-adic theory of the Macdonald, Matsumoto and Whittaker functions. Its major directions are as follows: 1) extending the theory of DAHA to arbitrary levels; 2) the affine Satake isomorphism and Hall functions via DAHA; 3) the spinor Dunkl operators for the Q-Toda equation; 4) applications to the nil-DAHA and q-Whittaker functions; 5) the technique of spinors in the differential theory and its applications to the AKZ-QMBP isomorphism theorem.

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arXiv2012

Rogers-Ramanujan type identities and Nil-DAHA

In the theory of the Nil-DAHA Fourier transform, the inner products of q-Hermite polynomials for the measure function multiplied by a level one theta function are the key. They are used to obtain expansions of products of any number of such theta functions in terms of the q-Hermite polynomials. An ample family of modular functions satisfying Rogers-Ramanujan type identities for arbitrary (reduced, twisted) affine root systems is obtained as an application. A relation to Rogers dilogarithm and Nahm's conjecture is discussed. Some of our q-series can be identified with known ones, but their interpretation seems new. Using that the q-Hermite polynomials are closely related to the Demazure level one characters in the twisted case (Sanderson, Ion), we outline a connection of our formulas to the level one integrable Kac-Moody modules and the coset theory. Several instances of the level-rank duality are provided.

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arXiv2012

One-dimensional nil-DAHA and Whittaker functions

This work, to be published in Transformation Groups in two parts, is devoted to the theory of nil-DAHA for the root system A_1 and its applications to symmetric and nonsymmetric (spinor) global q-Whittaker functions. These functions integrate the q-Toda eigenvalue problem and its Dunkl-type nonsymmetric version. The global symmetric function can be interpreted as the generating function of the Demazure characters for dominant weights, which describe the algebraic-geometric properties of the corresponding affine Schubert varieties. Its Harish-Chandra-type asymptotic expansion appeared directly related to the solution of the q-Toda eigenvalue problem obtained by Givental and Lee in the quantum K-theory of flag varieties. It provides an exact mathematical relation between the corresponding physics A-type and B-type models. The spinor global functions extend the symmetric ones to the case of all Demazure characters (not only those for the dominant weights); the corresponding Gromov-Witten theory is not known. The main result of the paper is a complete algebraic theory of these functions in terms of the induced modules of the core subalgebra of nil-DAHA. It is the first instance of the DAHA theory of canonical-crystal bases, quite non-trivial even for A_1.

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arXiv2012

Jones polynomials of torus knots via DAHA

We suggest a new construction for the Quantum Groups - Jones polynomials of torus knots in terms of the PBW theorem of DAHA for any root systems and weights (justified for type A). The main focus is on the DAHA super-polynomials, a stable 3-parametric type A variant of this construction. A connection is expected with the approach to super-polynomials due to Aganagic and Shakirov via the Macdonald polynomials at roots of unity and the Verlinde algebra. The duality conjecture for the DAHA super-polynomials is stated, essentially matching that due to Gukov and Stosic. A link to Khovanov-Rozansky polynomials is provided, including small N (for some torus knots). The hyper-polynomials of types B and C are defined, generalizing the Kauffman invariants and containing an extra parameter vs. the super-polynomials. The special values and other features of the DAHA super and hyper-polynomials are discussed; there are many examples in the paper.

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arXiv2010

Non-gatherable triples for classical affine root systems

This paper contains a complete description of minimal non-gatherable triangle triples in the lambda-sequences for the affine classical root systems and some claims for arbitrary (reduced) affine root systems. It continues our previous paper devoted to the non-affine case; interestingly, the affine theory clarifies the classification in the non-affine case. The lambda-sequences are associated with reduced decompositions (words) in affine Weyl groups. The existence of the non-gatherable triples is a combinatorial obstacle for using the technique of intertwiners in the theory of irreducible representations of the (double) affine Hecke algebras, complementary to their algebraic-geometric theory.

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arXiv2009

Whittaker limits of difference spherical functions

We introduce the (global) q-Whittaker function as the limit at t=0 of the q,t-spherical function extending the symmetric Macdonald polynomials to arbitrary eigenvalues. The construction heavily depends on the technique of the q-Gaussians developed by the author (and Stokman in the non-reduced case). In this approach, the q-Whittaker function is given by a series convergent everywhere, a kind of generating function for multi-dimensional q-Hermite polynomials (closely related to the level 1 Demazure characters). One of the applications is a q-version of the Shintani- Casselman- Shalika formula, which appeared directly connected with q-Mehta- Macdonald identities in terms of the Jackson integrals. This formula generalizes that of type A due to Gerasimov et al. to arbitrary reduced root systems. At the end of the paper, we obtain a q,t-counterpart of the Harish-Chandra asymptotic formula for the spherical functions, including the Whittaker limit.

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arXiv2009

A note on Artin's constant

We suggest a new approach to Artin's constant that leads to its representation as an infinite sum divided by another infinite sum. The same approach works well for Stephens' constant and higher rank Artin's constants. The main results are theoretical but there are interesting experimental and computational aspects.

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arXiv2008

Non-Gatherable Triples for Non-Affine Root Systems

This paper contains a complete description of minimal non-gatherable triangle triples in the lambda-sequences for the classical root systems, $F_4$ and $E_6$. Such sequences are associated with reduced decompositions (words) in affine and non-affine Weyl groups. The existence of the non-gatherable triples is a combinatorial obstacle for using the technique of intertwiners for an explicit description of the irreducible representations of the (double) affine Hecke algebras, complementary to their algebraic-geometric theory.

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arXiv2008

Non-semisimple Macdonald polynomials

The paper is mainly devoted to the irreducibility of the polynomial representation of the double affine Hecke algebra for an arbitrary reduced root systems and generic "central charge" q. The technique of intertwiners in the non-semisimple variant is the main tool. We introduce Macdonald's non-semisimple polynomials and use them to analyze the reducibility of the polynomial representation in terms of the affine exponents, counterparts of the classical Coxeter exponents. The focus is on the principal aspects of the technique of intertwiners, including related problems in the theory of reduced decompositions on affine Weyl groups.

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arXiv2004

Introduction to double Hecke algebras

This paper is based on the introduction to the monograph ``Double affine Hecke algebras'' to be published by Cambridge University Press. The connections with Knizhnik-Zamolodchikov equations, Kac-Moody algebras, tau-function, harmonic analysis on symmetric spaces, and special functions are discussed. The rank one case is considered in detail including the classification of Verlinde algebras and their deformations, Gauss-Selberg integrals and Gaussian sums, a topological interpretation of DAHA, a relation of the rational DAHA to sl(2), and applications to the diagonal coinvariants. The last three sections are devoted to relations of the general DAHAs to the p-adic affine Hecke algebras, trigonometric and rational DAHAs, and applications to the Harish-Chandra theory. The purpose of this introduction is a demonstration that DAHA can be considered as a natural formalization of the concept of the Fourier transform in mathematics and physics.

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arXiv2004

Irreducibility of Perfect Representations of Double Affine Hecke Algebras

We prove that the quotient of the polynomial representation of the double affine Hecke algebra (DAHA) by the radical of the duality pairing is always irreducible assuming that it is finite dimensional (apart from the roots of unity). We also find necessary and sufficient conditions for the radical to be zero, which is a q-generalization of Opdam's formula for the singular k-parameters with the multiple zero-eigenvalues of the corresponding Dunkl operators.

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arXiv2004

From Double Hecke algebra to Fourier transform

The paper contains a systematic theory of the one-dimensional Double Hecke algebra, including applications to the difference Fourier transform, Macdonald's polynomials, Gaussian sums at roots of unity, and Verlinde algebras. The main result is the classification of finite-dimensional representations for generic q and at roots of unity.

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arXiv2003

Diagonal Coinvariants and Double Affine Hecke Algebras

We establish a q-generalization of Gordon's theorem that the space of diagonal coinvariants has a quotient identified with a perfect representation of the rational double affine Hecke algebra. It leads to a simple proof of his theorem and relates it to the Weyl algebras at roots of unity. The universal double affine Hecke algebra and the corresponding universal double Dunkl operators acting in noncommutative polynomials in terms of two sets of variables are introduced.

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arXiv2002

Double Affine Hecke Algebras and Difference Fourier Transforms

In the paper, we introduce and calculate difference Fourier transforms on representations of the double affine Hecke algebras in polynomilas, polynomials multiplied by the Gaussian, and various spaces of delta-functions including finite-dimensional ones, give a general description of the semisimple representations with a special consideration of the GL-case, and then gradually restrict ourselves with spherical, pseudo-unitary, and Fourier-invariant representations. The latter generalize the Verlinde algebras and lead to new Gauss-Selberg sums and Macdonald's eta-type identities.

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