arXiv subjects

M. Gungormez

Publications and source records attributed to M. Gungormez.

10 recordsLinked to original sources

arXiv2010

Permutation Weights and Modular Poincare Polynomials for Affine Lie Algebras

Poincare Polynomial of a Kac-Moody Lie algebra can be obtained by classifying the Weyl orbit $W(ρ)$ of its Weyl vector $ρ$. A remarkable fact for Affine Lie algebras is that the number of elements of $W(ρ)$ is finite at each and every depth level though totally it has infinite number of elements. This allows us to look at $W(ρ)$ as a manifold graded by depths of its elements and hence a new kind of Poincare Polynomial is defined. We give these polynomials for all Affine Kac-Moody Lie algebras, non-twisted or twisted. The remarkable fact is however that, on the contrary to the ones which are classically defined,these new kind of Poincare polynomials have modular properties, namely they all are expressed in the form of eta-quotients. When one recalls Weyl-Kac character formula for irreducible characters, it is natural to think that this modularity properties could be directly related with Kac-Peterson theorem which says affine characters have modular properties. Another point to emphasize is the relation between these modular Poincare Polynomials and the Permutation Weights which we previously introduced for Finite and also Affine Lie algebras. By the aid of permutation weights, we have shown that Weyl orbits of an Affine Lie algebra are decomposed in the form of direct sum of Weyl orbits of its horizontal Lie algebra and this new kind of Poincare Polynomials count exactly these permutation weights at each and every level of weight depths.

math-ph↗

arXiv2010

Permutation Weights for A_r^(1) Lie Algebras

When it is based on Kac-Peterson form of Affine Weyl Groups, Weyl-Kac character formula could be formulated in terms of Theta functions and a sum over finite Weyl groups. We, instead, give a reformulation in terms of Schur functions which are determined by the so-called Permutation Weights and there are only a finite number of permutation weights at each and every order of weight depths . Affine signatures are expressed in terms of an index which by definition is based on a decomposition of horizontal weights in terms of some Fundamental Weights.

math-ph↗

arXiv2008

On Characters of F_4 Lie Algebra

In a previous work, we have given an explicit method to obtain irreducible characters of finite Lie algebras without referring to Weyl character formula. Irreducible characters of $G_2$ Lie algebra has been given as an example. The work is now extended to somewhat more complicated case of $F_4$ Lie algebra, in the same manner.

math-ph↗

arXiv2007

On the Calculation of Group Characters

It is known that characters of irreducible representations of finite Lie algebras can be obtained using theWeyl character formula including Weyl group summations which make actual calculations almost impossible except for a few Lie algebras of lower rank. By starting from the Weyl character formula, we show that these characters can be re-expressed without referring to Weyl group summations. Some useful technical points are given in detail for the instructive example of G2 Lie algebra.

math-ph↗

arXiv2005

On Poincare Polinomials of Hyperbolic Lie Algebras

Poincare polinomials of hyperbolic Lie algebras, which are given by $HA_2$ and $HA_3$ in the Kac's notation, are calculated explicitly. The results show that there is a significant form for hyperbolic Poincare polinomials. Their explicit forms tend to be seen as the ratio of a properly chosen finite Poincare polinomial and a polinomial of finite degree. To this end, by choosing the Poincare polinomials of $D_4$ and $D_5$ Lie algebras, we show that these polinomials come out to be of order 11 and 19 respectively for $HA_2$ and $HA_3$.

math-ph↗

arXiv2001

Weyl Orbit Characters and Schur Functions

For finite Lie algebras, it is shown that characters can be defined first for Weyl orbits and then for irreducible representations. For $A_N$ Lie algebras, weight multiplicities can then be calculated by only stating that characters are equivalent to Schur functions. This also means that to calculate characters there is no need to sum over Weyl groups. The compatibility with the Weyl character formula will however be shown.

math-ph↗

arXiv1997

An Explicit Construction of Casimir Operators and Eigenvalues : I

We give a general method to construct a complete set of linearly independent Casimir operators of a Lie algebra with rank N. For a Casimir operator of degree p, this will be provided by an explicit calculation of its symmetric coefficients $ g^{A_1,A_2,.. A_p}$. It is seen that these coefficients can be descibed by some rational polinomials of rank N. These polinomials are also multilinear in Cartan sub-algebra indices taking values from the set $I_0 = {1,2,.. N}$. The crucial point here is that for each degree one needs, in general, more than one polinomials. This in fact is related with an observation that the whole set of symmetric coefficients $ g^{A_1,A_2,.. A_p} $ is decomposed into sum subsets which are in one to one correspondence with these polinomials. We call these subsets clusters and introduce some indicators with which we specify different clusters. These indicators determine all the clusters whatever the numerical values of coefficients $g^{A_1,A_2,.. A_p}$ are. For any degree p, the number of clusters is independent of rank N. This hence allows us to generalize our results to any value of rank N. To specify the general framework explicit constructions of 4th and 5th order Casimir operators of $A_N$ Lie algebras are studied and all the polinomials which specify the numerical value of their coefficients are given explicitly.

hep-th↗

arXiv1997

The Higher Cohomologies of E_8 Lie Algebra

It is well known that anomaly cancellations for D_16 Lie algebra are at the root of the first string revolution. For E_8 Lie algebra, cancellation of anomalies is the principal fact leading to the existence of heterotic string. They are in fact nothing but the 6th order cohomologies of corresponding Lie algebras. Beyond 6th order, the calculations seem to require special care and it could be that their study will be worthwhile in the light of developments of the second string revolution. As we have shown in a recent article, for A_N Lie algebras, there is a method which are based on the calculations of Casimir eigenvalues. This is extended to E_8 Lie algebra in the present article. In the generality of any irreducible representation of E_8 Lie algebra, we consider 8th and 12th order cohomologies while emphasizing the diversities between the two. It is seen that one can respectively define 2 and 8 basic invariant polinomials in terms of which 8th and 12th order Casimir eigenvalues are always expressed as linear superpositions. All these can be easily investigated because each one of these invariant polinimials gives us a linear equation to calculate E_8 weight multiplicities. Our results beyond order 12 are not included here because they get more complicated though share the same characteristic properties with 12th order calculations.

hep-th↗

arXiv1997

The Complete Cohomology of $E_8$ Lie Algebra

It is shown, for any irreducible representation of $E_8$ Lie algebra, that eigenvalues of Casimir operators can be calculated in the form of invariant polinomials which are decomposed in terms of $A_8$ basis functions. The general method is applied for degrees 8,12 and 14 for which 2,8 and 19 invariant polinomials are obtained respectively. For each particular degree, these invariant polinomials can be taken to be $E_8$ basis functions in the sense that any Casimir operator of $E_8$ has always eigenvalues which can be expressed as linear superpositions of them. This can be investigated by showing that each one of these $E_8$ basis functions gives us a linear equation to calculate weight multiplicities.

math-ph↗

arXiv1997

An Explicit Construction of Casimir Operators and Eigenvalues:II

It is given a way of computing Casimir eigenvalues for Weyl orbits as well as for irreducible representations of Lie algebras. A kappa(s) number of polinomials which depend on rank N are obtained explicitly for A_N Casimir operators of order s where kappa(s) is the number of partitions of s into positive integers except 1. It is also emphasized that these eigenvalue polinomials prove useful in obtaining formulas to calculate weight multiplicities and in explicit calculations of the whole cohomology ring of Classical and also Exceptional Lie algebras.

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