scholarly journals Poincare series for the algebras of joint invariants and covariants of $n$ quadratic forms

2017 ◽  
Vol 9 (1) ◽  
pp. 57-62 ◽  
Author(s):  
N.B. Ilash
Keyword(s):  
Lie Group ◽  
Invariant Theory ◽  
Quadratic Forms ◽  
Laurent Series ◽  
Poincaré Series ◽  
Binary Forms ◽  
Poincare Series ◽  
Classical Invariant Theory ◽  
Joint Invariants ◽  
Classical Invariant

We consider one of the fundamental problems of classical invariant theory - the research of Poincare series for an algebra of invariants of Lie group $SL_2$. The first two terms of the Laurent series expansion of Poincare series at the point $z = 1$ give us important information about the structure of the algebra $\mathcal{I}_{d}.$ It was derived by Hilbert for the algebra ${\mathcal{I}_{d}=\mathbb{C}[V_d]^{\,SL_2}}$ of invariants for binary $d-$form (by $V_d$ denote the vector space over $\mathbb{C}$ consisting of all binary forms homogeneous of degree $d$). Springer got this result, using explicit formula for the Poincare series of this algebra. We consider this problem for the algebra of joint invariants $\mathcal{I}_{2n}=\mathbb{C}[\underbrace{V_2 \oplus V_2 \oplus \cdots \oplus V_2}_{\text{n times}}]^{SL_2}$ and the algebra of joint covariants $\mathcal{C}_{2n}=\mathbb{C}[\underbrace{V_2 {\oplus} V_2 {\oplus} \cdots {\oplus} V_2}_{\text{n times}}{\oplus}\mathbb{C}^2 ]^{SL_2}$ of $n$ quadratic forms. We express the Poincare series $\mathcal{P}(\mathcal{C}_{2n},z)=\sum_{j=0}^{\infty }\dim(\mathcal{C}_{2n})_{j}\, z^j$ and $\mathcal{P}(\mathcal{I}_{2n},z)=\sum_{j=0}^{\infty }\dim(\mathcal{I}_{2n})_{j}\, z^j$ of these algebras in terms of Narayana polynomials.   Also, for these algebras we calculate the degrees and asymptotic behavious of the degrees, using their Poincare series.

scholarly journals Hilbert polynomials of the algebras of $SL_ 2$-invariants

2018 ◽  
Vol 10 (2) ◽  
pp. 303-312
Author(s):  
N.B. Ilash
Keyword(s):  
Quadratic Forms ◽  
Hypergeometric Series ◽  
Hilbert Function ◽  
Dimensional Space ◽  
Hilbert Polynomial ◽  
Binary Forms ◽  
Hilbert Polynomials ◽  
Joint Invariants ◽  
Narayana Numbers ◽  
Classical Invariant

We consider one of the fundamental problems of classical invariant theory, the research of Hilbert polynomials for an algebra of invariants of Lie group $SL_2$. Form of the Hilbert polynomials gives us important information about the structure of the algebra. Besides, the coefficients and the degree of the Hilbert polynomial play an important role in algebraic geometry. It is well known that the Hilbert function of the algebra $SL_n$-invariants is quasi-polynomial. The Cayley-Sylvester formula for calculation of values of the Hilbert function for algebra of covariants of binary $d$-form $\mathcal{C}_{d}= \mathbb{C}[V_d\oplus \mathbb{C}^2]_{SL_2}$ (here $V_d$ is the $d+1$-dimensional space of binary forms of degree $d$) was obtained by Sylvester. Then it was generalized to the algebra of joint invariants for $n$ binary forms. But the Cayley-Sylvester formula is not expressed in terms of polynomials.In our article we consider the problem of computing the Hilbert polynomials for the algebras of joint invariants and joint covariants of $n$ linear forms and $n$ quadratic forms. We express the Hilbert polynomials $\mathcal{H} \mathcal{I}^{(n)}_1,i)=\dim(\mathcal{C}^{(n)}_1)_i, \mathcal{H}(\mathcal{C}^{(n)}_1,i)=\dim(\mathcal{C}^{(n)}_1)_i,$ $\mathcal{H}(\mathcal{I}^{(n)}_2,i)=\dim(\mathcal{I}^{(n)}_2)_i, \mathcal{H}(\mathcal{C}^{(n)}_2,i)=\dim(\mathcal{C}^{(n)}_2)_i$ of those algebras in terms of quasi-polynomial. We also present them in the form of Narayana numbers and generalized hypergeometric series.

scholarly journals Symmetry of Dressed Photon

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1283
Author(s):  
Hiroyuki Ochiai
Keyword(s):  
Theoretical Model ◽  
Homogeneous Space ◽  
Lie Group ◽  
Invariant Theory ◽  
Grassmann Manifold ◽  
Vector Spaces ◽  
Classical Invariant Theory ◽  
Lie Group Actions ◽  
Prehomogeneous Vector Spaces ◽  
Classical Invariant

Motivated by describing the symmetry of a theoretical model of dressed photons, we introduce several spaces with Lie group actions and the morphisms between them depending on three integer parameters n≥r≥s on dimensions. We discuss the symmetry on these spaces using classical invariant theory, orbit decomposition of prehomogeneous vector spaces, and compact reductive homogeneous space such as Grassmann manifold and flag variety. Finally, we go back to the original dressed photon with n=4,r=2,s=1.

scholarly journals ON THE LINEAR COMBINANTS OF A BINARY PENCIL

2009 ◽  
Vol 51 (3) ◽  
pp. 481-498 ◽  
Author(s):  
ABDELMALEK ABDESSELAM ◽  
JAYDEEP CHIPALKATTI
Keyword(s):  
Angular Momentum ◽  
Quantum Theory ◽  
Invariant Theory ◽  
Binary Forms ◽  
Classical Invariant Theory ◽  
Symbolic Method ◽  
Classical Invariant ◽  
Explicit Formulae

AbstractLet A, B denote binary forms of order d, and let 2r−1 = (A, B)2r−1 be the sequence of their linear combinants for $1 \le r \le \lfloor\frac{d+1}{2}\rfloor$. It is known that 1, 3 together determine the pencil {A + λ B}λ∈P1 and hence indirectly the higher combinants 2r−1. In this paper we exhibit explicit formulae for all r ≥ 3, which allow us to recover 2r−1 from the knowledge of 1 and 3. The calculations make use of the symbolic method in classical invariant theory, as well as the quantum theory of angular momentum. Our theorem pertains to the plethysm representation ∧2Sd for the group SL2. We give an example for the group SL3 to show that such a result may hold for other categories of representations.

scholarly journals ON THE VOLUME CONJECTURE FOR CLASSICAL SPIN NETWORKS

2012 ◽  
Vol 21 (03) ◽  
pp. 1250022 ◽  
Author(s):  
ABDELMALEK ABDESSELAM
Keyword(s):  
Invariant Theory ◽  
Classical Literature ◽  
Spin Networks ◽  
Classical Invariant Theory ◽  
Classical Spin ◽  
Volume Conjecture ◽  
Symbolic Method ◽  
Exact Determination ◽  
Classical Invariant

We prove an upper bound for the evaluation of all classical SU2 spin networks conjectured by Garoufalidis and van der Veen. This implies one half of the analogue of the volume conjecture which they proposed for classical spin networks. We are also able to obtain the other half, namely, an exact determination of the spectral radius, for the special class of generalized drum graphs. Our proof uses a version of Feynman diagram calculus which we developed as a tool for the interpretation of the symbolic method of classical invariant theory, in a manner which is rigorous yet true to the spirit of the classical literature.

scholarly journals A NOTE ON RATIONAL HOMOLOGICAL STABILITY OF AUTOMORPHISMS OF MANIFOLDS

2020 ◽  
Vol 71 (3) ◽  
pp. 1069-1079
Author(s):  
Manuel Krannich
Keyword(s):  
Invariant Theory ◽  
Characteristic Classes ◽  
Classical Invariant Theory ◽  
Homological Stability ◽  
Classical Invariant

Abstract By work of Berglund and Madsen, the rings of rational characteristic classes of fibrations and smooth block bundles with fibre $D^{2n}\sharp (S^n\times S^n)^{\sharp g}$, relative to the boundary, are for $2n\ge 6$ independent of $g$ in degrees $*\le (g-6)/2$. In this note, we explain how this range can be improved to $*\le g-2$ using cohomological vanishing results due to Borel and the classical invariant theory. This implies that the analogous ring for smooth bundles is independent of $g$ in the same range, provided the degree is small compared to the dimension.

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