A generalization of the Hall–Witt identity

Let Y → X be a finite normal cover of a wedge of n ≥ 3 circles. We prove that for any nonzero v ∈ H ₁(Y; Q) there exists a lift \(\widetilde F\) to Y of a basepoint-preserving homotopy equivalence F: X → X such that the set of iterates \(\left\{ {{{\widetilde F}^d}\left( v \right)} \right\}:d \in \mathbb{Z} \subseteq {H_1}\left( {Y,\mathbb{Q}} \right)\) is infinite. The main achievement of this paper is the use of representation theory to prove the existence of a purely topological object that seems to be inaccessible via topology.     

Resolutions of the identity in Fréchet spaces

It is a classical result that every Bade -complete Boolean algebra of (selfadjoint) projections in a separable Hilbert space coincides with the projections forming the resolution of the identity of some bounded selfadjoint operator. This result is extended to the setting of separable Fréchet spaces. Namely, every Bade -complete Boolean algebra of projections in such a space coincides with the resolution of the identity of some (continuous) scalar-type spectral operator having spectrum a compact subset of.     

A Kazdan–Warner type identity for the σk curvature

We prove a Kazdan–Warner type identity involving the ${\sigma }_k$ curvature and a conformal Killing vector field on a compact manifold. Our method also works to provide a unified proof for the necessary conditions in the Christoffel–Minkowski problem. To cite this article: Z.-C. Han, C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

Energy identity of the heat flow of H-systems at finite singular time

It is well known that there exists a global solution to the heat flow of H-systems.If the solution satisfies a certain energy inequality,it is global regular with at most finitely many singularities. Under the same energy inequality,we can show the energy identity of the heat flow of H-systems at finite singular time.The most interesting thing in our proof is that we find the singular points can only occur in the interior of the set in some sense.     

A polynomial identity for the bilinear operation in Lie–Yamaguti algebras

We use computer algebra to demonstrate the existence of a multilinear polynomial identity of degree 8 satisfied by the bilinear operation in every Lie–Yamaguti algebra. This identity is a consequence of the defining identities for Lie–Yamaguti algebras, but is not a consequence of anticommutativity. We give an explicit form of this identity as an alternating sum over all permutations of the variables in a nonassociative polynomial with 8 terms. Our computations show that no such identities exist in degrees less than 8.     

Poisson kernel is the unique approximate identity,asymptotically multiplicative on H∞

Let for anyf H(R), where (x): = ^–1(x^–1). Then (x) P (x + h) for some h R and > 0; P denotes the Poisson kernel.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova Akademii Nauk SSSR, Vol. 170, pp. 82–89, 1989.     

Estimation of intra-cluster correlation coefficient via the failure of Bartlett’s second identity

A new means of estimating the correlation coefficient for cluster binary data in the regression settings is introduced. The creation of this method is founded upon the violation of Bartlett’s second identity when adopting the binomial distributions to model binary data that are correlated. The new methodology applies to any sensible link functions that connect the success probability and covariates. One can easily implement the procedure by using any statistical software providing the naïve and the sandwich covariance matrices for regression parameter estimates. Simulations and real data analyses are used to demonstrate the efficacy of our new procedure.     

The fractional supertrace identity and its application to the super Jaulent–Miodek hierarchy

In this paper, a fractional supertrace identity on superalgebras and Hamiltonian structure of the fractional soliton equation hierarchy are presented by using the modified Riemann–Liouville derivative and exterior derivatives of fractional orders. As applications, we get the fractional super Jaulent–Miodek (JM) hierarchy and its super Hamiltonian structure by using fractional supertrace identity. This method can be used to get more fractional super hierarchies.     

Counting the number of indecomposable representations and a q-analogue of the Weyl-Kac denominator identity of type _n

By using Frobenius maps and F-stable representations,we count the number of isomor- phism classes of indecomposable representations with the fixed dimension vector of a species of type _n over a finite field,first,and then,as an application,give a q-analogue of the Weyl-Kac denominator identity of type _n.     

Bilateral truncated Jacobi’s identity

Recently, Andrews and Merca considered the truncated version of Euler’s pentagonal number theorem and obtained a non-negative result on the coefficients of this truncated series. Guo and Zeng showed the coefficients of two truncated Gauss’ identities are non-negative and they conjectured that truncated Jacobi’s identity also has non-negative coefficients. Mao provided a proof of this conjecture by using an algebraic method. In this paper, we consider bilateral truncated Jacobi’s identity and show that when the upper and lower bounds of the summation satisfy some certain restrictions, then this bilateral truncated identity has non-negative coefficients. As a corollary, we show the conjecture of Guo and Zeng holds. Our proof is purely combinatorial and mainly based on a bijection for Jacobi’s identity.     

A plactic algebra of extremal weight crystals and the Cauchy identity for Schur operators

We give a new bijective interpretation of the Cauchy identity for Schur operators which is a commutation relation between two formal power series with operator coefficients. We introduce a plactic algebra associated with the Kashiwara’s extremal weight crystals over the Kac–Moody algebra of type A _+∞, and construct a Knuth type correspondence preserving the plactic relations. This bijection yields the Cauchy identity for Schur operators as a homomorphic image of its associated identity for plactic characters of extremal weight crystals, and also recovers Sagan and Stanley’s correspondence for skew tableaux as its restriction.     

On three-term recurrence and Christoffel–Darboux identity for orthogonal rational functions on the real line

First, we give an algebraic proof to the Christoffel–Darboux identity of formal orthogonal rational functions on the real line by exposing some underlying algebraic properties. This proof does not involve the three-term recurrence relationship. Besides, it is shown that if a family of rational functions satisfies the Christoffel–Darboux relation, then it also admits a three-term recurrence relationship. Thus, the equivalence between both relations is revealed.     

Component-trace identity for Hamiltonian structure of the integrable couplings of the Giachetti–Johnson (GJ) hierarchy and coupling integrable couplings

The integrable couplings of the Giachetti–Johnson (GJ) hierarchy are obtained by the perturbation approach and its Hamiltonian structure is given for the first time by component-trace identities. Then, coupling integrable couplings of the GJ hierarchy are worked out.     

Darboux’s identity and its analogs

Let us choose a positive integern and denoteF(x, y)= , wheref(·) andg(·) are arbitrary sufficiently smooth functions. Three different proofs of the validity of the relation

A generalization of Clausen’s identity

The paper gives an extension of Clausen’s identity to the square of any Gauss hypergeometric function. Accordingly, solutions of the related third-order linear differential equation are found in terms of certain bivariate series that can reduce to ₃F₂ series similar to those in Clausen’s identity. The general contiguous variation of Clausen’s identity is found as well. The related Chaundy’s identity is generalized without any restriction on the parameters of the Gauss hypergeometric function. The special case of dihedral Gauss hypergeometric functions is underscored.     

A generalization of Menonʼs identity

In this note we give a generalization of the well-known Menon?s identity. This is based on applying the Burnside?s lemma to a certain group action.     

New series representations for Jacobi?s triple product identity and more via the q-Markov method

We derive new series representations for Jacobi?s triple product identity, the q-binomial theorem, q-analogs of the exponential function, and more with several special cases using the q-Markov-WZ method.