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N. I. Stoilova

Publications and source records attributed to N. I. Stoilova.

At least 19 recordsLinked to original sources
arXiv2026

The parity operator for parafermions and parabosons

In this paper we reexamine the definition of parafermions and parabosons by means of Green's triple relations, and extend these relations by including a parity operator $P$ which is also determined by means of triple relations. As a consequence, we are dealing with new algebraic structures. It is shown that the algebra underlying a set of $n$ parafermions together with $P$ is the orthogonal Lie algebra $so(2n+2)$. The Fock spaces correspond to particular irreducible representations of $so(2n+2)$, and the action of $P$ in these spaces leads to interesting observations. Next, we show that the algebra underlying a set of $n$ parabosons together with $P$ is the orthosymplectic Lie superalgebra $osp(2|2n)$. In this case, the Fock spaces correspond to certain irreducible infinite-dimensional representations of $osp(2|2n)$. Both for parafermions and parabosons the spectrum of $P$ is closely related to the so-called order of statistics $p$, introduced by Green.

math-ph↗
arXiv2025

A class of representations of the $\mathbb{Z}_2\times\mathbb{Z}_2$-graded special linear Lie superalgebra $\mathfrak{sl}(m_1+1,m_2|n_1,n_2)$ and quantum statistics

The description of the $\mathbb{Z}_2\times\mathbb{Z}_2$-graded special linear Lie superalgebra $\mathfrak{sl} (m_1+1,m_2|n_1,n_2)$ is carried out via generators $a_1^\pm,\ldots, a_{m_1+m_2+n_1+n_2}^\pm$ that satisfy triple relations and are called creation and annihilation operators. With respect to these generators, a class of Fock type representations of $\mathfrak{sl} (m_1+1,m_2|n_1,n_2)$ is constructed. The properties of the underlying statistics are discussed and its Pauli principle is formulated.

math-ph↗
arXiv2025

$\mathbb{Z}_2^3$-grading of the Lie algebra $G_2$ and related color algebras

We present a special and attractive basis for the exceptional Lie algebra $G_2$, which turns $G_2$ into a $\mathbb{Z}_2^3$-graded Lie algebra. There are two basis elements for each degree of $\mathbb{Z}_2^3\setminus\{(0,0,0)\}$, thus yielding 14 basis elements. We give a general and simple closed form expression for commutators between these basis elements. Next, we use this $\mathbb{Z}_2^3$-grading in order to examine graded color algebras. Our analysis yields three different $\mathbb{Z}_2^3$-graded color algebras of type $G_2$. Since the $\mathbb{Z}_2^3$-grading is not compatible with a Cartan-Weyl basis of $G_2$, we also study another grading of $G_2$. This is a $\mathbb{Z}_2^2$-grading, compatible with a Cartan-Weyl basis, and for which we can also construct a $\mathbb{Z}_2^2$-graded color algebra of type $G_2$.

math-ph↗
arXiv2025

$\mathbf{{\mathbb Z}_2\ \times {\mathbb Z}_2}$-graded Lie (super)algebras and generalized quantum statistics

We present systems of parabosons and parafermions in the context of Lie algebras, Lie superalgebras, $\mathbf{{\mathbb Z}_2\ \times {\mathbb Z}_2}$-graded Lie algebras and $\mathbf{{\mathbb Z}_2\ \times {\mathbb Z}_2}$-graded Lie superalgebras. For certain relevant $\mathbf{{\mathbb Z}_2\ \times {\mathbb Z}_2}$-graded Lie algebras and $\mathbf{{\mathbb Z}_2\ \times {\mathbb Z}_2}$-graded Lie superalgebras, some structure theory in terms of roots and root vectors is developed. The short root vectors of these algebras are identified with parastatistics operators. For the $\mathbf{{\mathbb Z}_2\ \times {\mathbb Z}_2}$-graded Lie algebra $so_q(2n+1)$, a system consisting of two ensembles of parafermions satisfying relative paraboson relations are introduced. For the $\mathbf{{\mathbb Z}_2\ \times {\mathbb Z}_2}$-graded Lie superalgebra $osp(1,0|2n_1,2n_2)$, a system consisting of two ensembles of parabosons satisfying relative parafermion relations are introduced.

math-ph↗
arXiv2024

Generalized boson and fermion operators with a maximal total occupation property

We propose a new generalization of the standard (anti-)commutation relations for creation and annihilation operators of bosons and fermions. These relations preserve the usual symmetry properties of bosons and fermions. Only the standard (anti-)commutator relation involving one creation and one annihilation operator is deformed by introducing fractional coefficients, containing a positive integer parameter $p$. The Fock space is determined by the classical definition. The new relations are chosen in such a way that the total occupation number in the system has the maximum value $p$. From the actions of creation and annihilation operators in the Fock space, a group theoretical framework is determined, and from here the correspondence with known particle statistics is established.

math-ph↗
arXiv2024

Matrix structure of classical ${\mathbb Z}_2 \times {\mathbb Z}_2$ graded Lie algebras

A ${\mathbb Z}_2\times{\mathbb Z}_2$-graded Lie algebra $\mathfrak g$ is a ${\mathbb Z}_2\times{\mathbb Z}_2$-graded algebra $\mathfrak g$ with a bracket $[|. , . |]$ that satisfies certain graded versions of the symmetry and Jacobi identity. In particular, despite the common terminology, $\mathfrak g$ is not a Lie algebra. We construct classes of ${\mathbb Z}_2\times{\mathbb Z}_2$-graded Lie algebras corresponding to the classical Lie algebras, in terms of their defining matrices. For the ${\mathbb Z}_2\times{\mathbb Z}_2$-graded Lie algebra of type $A$, the construction coincides with the previously known class. For the ${\mathbb Z}_2\times{\mathbb Z}_2$-graded Lie algebra of type $B$, $C$ and $D$ our construction is new and gives rise to interesting defining matrices closely related to the classical ones but undoubtedly different. We also give some examples and possible applications to parastatistics.

math-ph↗
arXiv2024

Orthosymplectic $Z_2\times Z_2$-graded Lie superalgebras and parastatistics

A $Z_2\times Z_2$-graded Lie superalgebra $g$ is a $Z_2\times Z_2$-graded algebra with a bracket $[.,.]$ that satisfies certain graded versions of the symmetry and Jacobi identity. In particular, despite the common terminology, $g$ is not a Lie superalgebra. We construct the most general orthosymplectic $Z_2\times Z_2$-graded Lie superalgebra $osp(2m_1+1,2m_2|2n_1,2n_2)$ in terms of defining matrices. A special case of this algebra appeared already in work of Tolstoy in 2014. Our construction is based on the notion of graded supertranspose for a $Z_2\times Z_2$-graded matrix. Since the orthosymplectic Lie superalgebra $osp(2m+1|2n)$ is closely related to the definition of parabosons, parafermions and mixed parastatistics, we investigate here the new parastatistics relations following from $osp(2m_1+1,2m_2|2n_1,2n_2)$. Some special cases are of particular interest, even when one is dealing with parabosons only.

math-ph↗
arXiv2023

On classical $Z_2 \times Z_2$-graded Lie algebras

We construct classes of $Z_2 \times Z_2$-graded Lie algebras corresponding to the classical Lie algebras, in terms of their defining matrices. For the $Z_2 \times Z_2$-graded Lie algebra of type $A$, the construction coincides with the previously known class. For the $Z_2 \times Z_2$-graded Lie algebra of type $B$, $C$ and $D$ our construction is new and gives rise to interesting defining matrices closely related to the classical ones but undoubtedly different. We also give some examples and possible applications to parastatistics.

math-ph↗
arXiv2021

A Klein operator for paraparticles

It has been known for a long time that there are two non-trivial possibilities for the relative commutation relations between a set of $m$ parafermions and a set of $n$ parabosons. These two choices are known as ``relative parafermion type'' and ``relative paraboson type'', and correspond to quite different underlying algebraic structures. In this short note we show how the two possibilities are related by a so-called Klein transformation.

math-ph↗
arXiv2020

Partition functions and thermodynamic properties of paraboson and parafermion systems

New formulas are given for the grand partition function of paraboson systems of order p with n orbitals and parafermion systems of order p with m orbitals. These formulas allow the computation of statistical and thermodynamic functions for such systems. We analyze and discuss the average number of particles on an orbital, and the average number of particles in the system. For some special cases (identical orbital energies, or equidistant orbital energies) we can simplify the grand partition functions and describe thermodynamic properties in more detail. Some specific properties are also illustrated in plots of thermodynamic functions.

cond-mat.stat-mech↗
arXiv2019

The $Z_2 \times Z_2$-graded general linear Lie superalgebra

We present a novel realisation of the $\mathbb{Z}_2\times\mathbb{Z}_2$-graded Lie superalgebra $\mathfrak{gl}(m_1,m_2|n_1,n_2)$ inside an algebraic extension of the enveloping algebra of the $\mathbb{Z}_2$-graded Lie superalgebra $\mathfrak{gl}(m|n)$, with $m=m_1+m_2$ and $n=n_1+n_2$. A consequence of this realisation is that the representations of $\mathfrak{gl}(m|n)$ "lift up" to representations of $\mathfrak{gl}(m_1,m_2|n_1,n_2)$, with matrix elements differing only by a sign, which we are able to characterise concisely.

math-ph↗
arXiv2019

On superdimensions of some infinite-dimensional irreducible representations of $osp(m|n)$

In a recent paper characters and superdimension formulas were investigated for the class of representations with Dynkin labels $[0,\ldots,0,p]$ of the Lie superalgebra $osp(m|n)$. Such representations are infinite-dimensional, and of relevance in supergravity theories provided their superdimension is finite. We have shown that the superdimension of such representations coincides with the dimension of a $so(m-n)$ representation. In the present contribution, we investigate how this $osp(m|n)\sim so(m-n)$ correspondence can be extended to the class of $osp(2m|2n)$ representations with Dynkin labels $[0,\ldots,0,q,p]$.

math-ph↗
arXiv2019

Representations of the Lie superalgebra $B(\infty,\infty)$ and parastatistics Fock spaces

The algebraic structure generated by the creation and annihilation operators of a system of m parafermions and n parabosons, satisfying the mutual parafermion relations, is known to be the Lie superalgebra osp(2m+1|2n). The Fock spaces of such systems are then certain lowest weight representations of osp(2m+1|2n). In the current paper, we investigate what happens when the number of parafermions and parabosons becomes infinite. In order to analyze the algebraic structure, and the Fock spaces, we first need to develop a new matrix form for the Lie superalgebra B(n,n)=osp(2n+1|2n), and construct a new Gelfand-Zetlin basis of the Fock spaces in the finite rank case. The new structures are appropriate for the situation $n\rightarrow\infty$. The algebra generated by the infinite number of creation and annihilation operators is $B(\infty,\infty)$, a well defined infinite rank version of the orthosymplectic Lie superalgebra. The Fock spaces are lowest weight representations of $B(\infty,\infty)$, with a basis consisting of particular row-stable Gelfand-Zetlin patterns.

math-ph↗
arXiv2019

On characters and superdimensions of some infinite-dimensional irreducible representations of $\mathfrak{osp}(m|n)$

Chiral spinors and self dual tensors of the Lie superalgebra $\mathfrak{osp}(m|n)$ are infinite dimensional representations belonging to the class of representations with Dynkin labels $[0,\ldots,0,p]$. We have shown that the superdimension of $[0,\ldots,0,p]$ coincides with the dimension of a $\mathfrak{so}(m-n)$ representation. When the superdimension is finite, these representations could play a role in supergravity models. Our technique is based on expansions of characters in terms of supersymmetric Schur functions. In the process of studying these representations, we obtain new character expansions.

math-ph↗
arXiv2017

The Z_2 x Z_2-graded Lie superalgebra pso(2m+1|2n) and new parastatistics representations

When the relative commutation relations between a set of m parafermions and n parabosons are of ``relative parafermion type'', the underlying algebraic structure is the classical orthosymplectic Lie superalgebra osp(2m+1|2n). The relative commutation relations can also be chosen differently, of ``relative paraboson type''. In this second case, the underlying algebraic structure is no longer an ordinary Lie superalgebra, but a Z_2 x Z_2$-graded Lie superalgebra, denoted here by pso(2m+1|2n). The identification of this new algebraic structure was performed by Tolstoy, amongst others. In the present paper, we investigate the subalgebra structure of pso(2m+1|2n). This allows us to study the parastatistics Fock spaces for this new set of m+n para-operators, as they correspond to lowest weight representations of pso(2m+1|2n). Our main result is the construction of these Fock spaces, with a complete labeling of the basis vectors and an explicit action of the para-operators on these basis vectors.

math-ph↗
arXiv2017

Extension of the osp(m|n)~ so(m-n) Correspondence to the Infinite-Dimensional Chiral Spinors and Self Dual Tensors

The spinor representations of the orthosymplectic Lie superalgebras osp(m|n) are considered and constructed. These are infinite-dimensional irreducible representations, of which the superdimension coincides with the dimension of the spinor representation of so(m-n). Next, we consider the self dual tensor representations of osp(m|n) and their generalizations: these are also infinite-dimensional and correspond to the highest irreducible component of the $p^{th}$ power of the spinor representation. We determine the character of these representations, and deduce a superdimension formula. From this, it follows that also for these representations the osp(m|n)~ so(m-n) correspondence holds.

math-ph↗