Homological properties of generic matrix rings

It is shown that the ring of two 2×2 generic matrices over a field has infinite global dimension. It is also proved that there is a non-free projective module over that ring. Finally, the authors show that the trace ring of that generic matrix ring is an iterated Ore extension from which it follows that the trace ring has global dimension five and that the finitely-generated projective modules are stably free.     

Commutators of trace zero matrices over principal ideal rings

We prove that for every trace zero square matrix A of size at least 3 over a principal ideal ring R, there exist trace zero matrices X, Y over R such that XY ? YX = A. Moreover, we show that X can be taken to be regular mod every maximal ideal of R. This strengthens our earlier result that A is a commutator of two matrices (not necessarily of trace zero), and in addition, the present proof is simpler than the earlier one.     

Trace formulae and applications to class numbers

In this paper we compute the trace formula for Hecke operators acting on automorphic forms on the hyperbolic 3-space for the group PSL₂( $\mathcal{O}_K $ ) with $\mathcal{O}_K $ being the ring of integers of an imaginary quadratic number field K of class number H _K > 1. Furthermore, as a corollary we obtain an asymptotic result for class numbers of binary quadratic forms.     

保持交换环上两类矩阵运算的映射

主要针对交换环上两类矩阵的保持问题进行展开:(1)刻画了交换环上全矩阵空间和上三角形矩阵空间的保持反对合矩阵映射的形式.(2)研究了交换环上n阶上三角形矩阵空间的保持伴随矩阵映射的形式.     

Hankel matrices and quadratic forms

A characterization of finite Hankei matrices is given and it is shown that such matrices arise naturally as matrix representations of scaled trace forms of field extensions and etale algebras. An algorithm is given for calculating the signature and the Hasse invariant of these scaled trace forms.     

Matrix Models from Operators and Topological Strings, 2

The quantization of mirror curves to toric Calabi–Yau threefolds leads to trace class operators, and it has been conjectured that the spectral properties of these operators provide a non-perturbative realization of topological string theory on these backgrounds. In this paper, we find an explicit form for the integral kernel of the trace class operator in the case of local \({{\mathbb{P}}^1 \times {\mathbb{P}}^1}\), in terms of Faddeev’s quantum dilogarithm. The matrix model associated to this integral kernel is an \({O(2)}\) model, which generalizes the ABJ(M) matrix model. We find its exact planar limit, and we provide detailed evidence that its \({1/N}\) expansion captures the all genus topological string free energy on local \({{\mathbb{P}}^1 \times {\mathbb{P}}^1}\).     

The trace graph of the matrix ring over a finite commutative ring

Let R be a commutative ring and let \({n >1}\) be an integer. We introduce a simple graph, denoted by \({\Gamma_t(M_n(R))}\), which we call the trace graph of the matrix ring \({M_n(R)}\), such that its vertex set is \({M_n(R)^{\ast}}\) and such that two distinct vertices A and B are joined by an edge if and only if \({{\rm Tr} (AB)=0}\) where \({ {\rm Tr} (AB)}\) denotes the trace of the matrix AB. We prove that \({\Gamma_t(M_n(R))}\) is connected with \({{\rm diam}(\Gamma_{t}(M_{n}(R)))=2}\) and \({{\rm gr} (\Gamma_t(M_n(R)))=3}\). We investigate also the interplay between the ring-theoretic properties of R and the graph-theoretic properties of \({\Gamma_t(M_n(R))}\). Hence, we use the notion of the irregularity index of a graph to characterize rings with exactly one nontrivial ideal.     

Linear programming with matrix variables

Linear programming is formulated with the vector variable replaced by a matrix variable, with the inner product defined using trace of a matrix. The theorems of Motzkin, Farkas (both homogeneous and inhomogeneous forms), and linear programming duality thus extend to matrix variables. Duality theorems for linear programming over complex spaces, and over quaternion spaces, follow as special cases.     

The invariance of elementary symmetric functions

The general problem considered is: what linear transformations on matrices preserve certain prescribed invariants or other properties of the matrices? Specifically, the forms of the following linear transformations are determined: the linear transformations that hold either the trace or the second elementary symmetric function of the eigenvalues of each matrix fixed, and in addition preserve either the determinant, or the permanent, or an elementary symmetric function of the squares of the singular values, or the property of being a rank 1 matrix or a unitary matrix.     

Matrices as sums of squares

How many squares are needed to represent elements in a matrix ring? A matrix over a field of characteristic two is a sum of two squares if and only if its trace is a square, otherwise it is not a sum of squares. Any proper matrix over a field of characteristic not two is always a sum of three squares. If the order of a matrix is even the matrix is a sum of two squares, but an odd order matrix which is q times the identity matrix is a sum of two squares if and only ifq is a sum of two squares in the field. Matrices of order 2,3 and 4 over the integers can always be written as the sum of three squares.     

Chiral Trace Relations in $$\mathcal{N}=2^*$$ Supersymmetric Gauge Theories

We analyze the chiral ring in Ω-deformed \(\mathcal{N}=2^*\) supersymmetric gauge theories. Applying localization techniques, we derive closed identities for the vacuum expectation values of chiral trace operators. In the SU(2) case, we provide an AGT framework to identify chiral trace operators and the system of local integrals of motion in the related two-dimensional conformal field theory. In this setup, we predict some universal terms appearing in chiral trace identities.     

Canonical Tasks, Environments and Models for Social Simulation

The purpose of this paper is to propose and describe an alternative to an overarching theory for social simulation research. The approach is an analogy of the canonical matrix. Canonical matrices are matrices of a standard form and there are transformations that can be performed on other matrices to show that they can be made into canonical matrices. All matrices which, by means of allowable operations, can be transformed into a canonical matrix have the properties of the canonical matrix. This conception of canonicity is applied to three models in the computational organization theory literature. The models are mapped into their respective canonical forms. The canonical forms are shown to be transitively subsumptive (i.e., one of them is nested within a second which itself is nested within the third. The consequences of these subsumption relations are investigated by means of simulation experiments.     

he Ring of $\mathcal {}$-covariants

Starting from the invariant theory of binary forms, we extend the classical notion of covariants and introduce the ring of \(\mathcal {T}\)-covariants. This ring consists of maps defined on a ring of polynomials in one variable which commute with all the translation operators. We study this ring and we show some of its meaningful features. We state an analogue of the classical Hermite reciprocity law, and recover the Hilbert series associated with a suitable double grading via the elementary theory of partitions. Together with classical covariants of binary forms other remarkable mathematical notions, such as orthogonal polynomials and cumulants, turn out to have a natural and simple interpretation in this algebraic framework. As a consequence, a Heine integral representation for the cumulants of a random variable is obtained.     

An invariant trace formula for the universal covering group of SL(2,ℝ)

Automorphic forms of arbitrary real weight can be considered as functions on the universal covering group of SL(2, ). In this situation, we prove an invariant form of the Selberg trace formula for Hecke operators. For this purpose, the Fourier transforms of weightet orbital integrals, obtained by J. Arthur, R. Herb and P. Sally, jr., are explicitly calculated. Our formula does not follow from Arthur's invariant trace formula, since the group has infinite centre, and vector-valued automorphic forms with respect to non-congruence lattices are considered.     

Drazin inverses and canonical forms in Mn(Zh)

The existence and construction of the Drazin inverse of a square matrix over the ring $\text{Z}\text{h}$ is considered. The canonical forms of matrices over this ring are used to facilitate the computation of this type of generalized inverse.     

The moore-penrose inverse of a matrix over a semi-simple artinian ring with respect to an involution

Our result in "The Moore-Penrose inverse of a matrix over a semi-simple artinian ring" [2], obtained with respect to a special class of involutions is generalized to arbitrary involutions on the set of all finite matrices.     

Trees, parking functions, syzygies, and deformations of monomial ideals

For a graph , we construct two algebras whose dimensions are both equal to the number of spanning trees of . One of these algebras is the quotient of the polynomial ring modulo certain monomial ideal, while the other is the quotient of the polynomial ring modulo certain powers of linear forms. We describe the set of monomials that forms a linear basis in each of these two algebras. The basis elements correspond to -parking functions that naturally came up in the abelian sandpile model. These ideals are instances of the general class of monotone monomial ideals and their deformations. We show that the Hilbert series of a monotone monomial ideal is always bounded by the Hilbert series of its deformation. Then we define an even more general class of monomial ideals associated with posets and construct free resolutions for these ideals. In some cases these resolutions coincide with Scarf resolutions. We prove several formulas for Hilbert series of monotone monomial ideals and investigate when they are equal to Hilbert series of deformations. In the appendix we discuss the abelian sandpile model.

     

Annihilating polynomials, étale algebras, trace forms and the Galois number

Annihilating polynomials for quadratic forms in the Witt ring are obtained via an étale algebra interpretation of the Burnside ring together with a homomorphism to the Witt ring.     

On the sum powers of matrices

A theorem of Lagrange says that every natural number is the sum of 4 squares. M. Newman proved that every integral n by n matrix is the sum of 8 (-1)ⁿ squares when n is at least 2. He asked to generalize this to the rings of integers of algebraic number fields. We show that an n by n matrix over a a commutative R with 1 is the sum of squares if and only if its trace reduced modulo 2Ris a square in the ring R/2R. It this is the case (and n is at least 2), then the matrix is the sum of 6 squares (5 squares would do when n is even). Moreover, we obtain a similar result for an arbitrary ring R with 1. Answering another question of M. Newman, we show that every integral n by n matrix is the sum of ten k-th powers for all sufficiently large n. (depending on k).