scholarly journals Veldkamp spaces: From (Dynkin) diagrams to (Pauli) groups

2017 ◽  
Vol 14 (05) ◽  
pp. 1750080
Author(s):  
Metod Saniga ◽  
Frédéric Holweck ◽  
Petr Pracna
Keyword(s):  
Incidence Structure ◽  
Polar Space ◽  
Exceptional Point ◽  
Specific Point ◽  
Fano Plane ◽  
Magic Square ◽  
Dynkin Diagrams ◽  
Pauli Matrix ◽  
Matrix Formula ◽  
Point Line

Regarding a Dynkin diagram as a specific point-line incidence structure (where each line has just two points), one can associate with it a Veldkamp space. Focusing on extended Dynkin diagrams of type [Formula: see text], [Formula: see text], it is shown that the corresponding Veldkamp space always contains a distinguished copy of the projective space PG[Formula: see text]. Proper labeling of the vertices of the diagram (for [Formula: see text]) by particular elements of the two-qubit Pauli group establishes a bijection between the 15 elements of the group and the 15 points of the PG[Formula: see text]. The bijection is such that the product of three elements lying on the same line is the identity and one also readily singles out that particular copy of the symplectic polar space [Formula: see text] of the PG[Formula: see text] whose lines correspond to triples of mutually commuting elements of the group; in the latter case, in addition, we arrive at a unique copy of the Mermin–Peres magic square. In the case of [Formula: see text], a more natural labeling is that in terms of elements of the three-qubit Pauli group, furnishing a bijection between the 63 elements of the group and the 63 points of PG[Formula: see text], the latter being the maximum projective subspace of the corresponding Veldkamp space; here, the points of the distinguished PG[Formula: see text] are in a bijection with the elements of a two-qubit subgroup of the three-qubit Pauli group, yielding a three-qubit version of the Mermin–Peres square. Moreover, save for [Formula: see text], each Veldkamp space is also endowed with some exceptional point(s). Interestingly, two such points in the [Formula: see text] case define a unique Fano plane whose inherited three-qubit labels feature solely the Pauli matrix [Formula: see text].

Maximum-Sized Matroids with No Minors Isomorphic to U2,5, F7, F−7 or P7

2001 ◽  
Vol 10 (6) ◽  
pp. 531-542
Author(s):  
STEFAN T. MECAY
Keyword(s):  
Fano Plane ◽  
Point Line

Let [Mscr ] be the class of simple matroids which do not contain the 5-point line U2,5, the Fano plane F7, the non-Fano plane F−7, or the matroid P7 as minors. Let h(n) be the maximum number of points in a rank-n matroid in [Mscr ]. We show that h(2) = 4, h(3) = 7, and h(n) = (n+12) for n [ges ] 4, and we also find all the maximum-sized matroids for each rank.

scholarly journals Pseudo-embeddings of the (point, k-spaces)-geometry of PG(n, 2) and projective embeddings of DW(2n − 1, 2)

2019 ◽  
Vol 19 (1) ◽  
pp. 41-56 ◽  
Author(s):  
Bart De Bruyn
Keyword(s):  
Local Structure ◽  
Polar Space ◽  
Line Geometry ◽  
Projective Embedding ◽  
Dual Polar Space ◽  
Point Line

Abstract We classify all homogeneous pseudo-embeddings of the point-line geometry defined by the points and k-dimensional subspaces of PG(n, 2), and use this to study the local structure of homogeneous full projective embeddings of the dual polar space DW(2n − 1, 2). Our investigation allows us to distinguish n possible types for such homogeneous embeddings. For each of these n types, we construct a homogeneous full projective embedding of DW(2n − 1, 2).

scholarly journals Taxonomy of Three-Qubit Mermin Pentagrams

Symmetry ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 534
Author(s):  
Metod Saniga ◽  
Frédéric Holweck ◽  
Hamza Jaffali
Keyword(s):  
Polar Space ◽  
Fano Plane

Given the fact that the three-qubit symplectic polar space features three different kinds of observables and each of its labeled Fano planes acquires a definite sign, we found that there are 45 distinct types of Mermin pentagrams in this space. A key element of our classification is the fact that any context of such pentagram is associated with a unique (positive or negative) Fano plane. Several intriguing relations between the character of pentagrams’ three-qubit observables and ‘valuedness’ of associated Fano planes are pointed out. In particular, we find two distinct kinds of negative contexts and as many as four positive ones.

scholarly journals Quantum contextual finite geometries from dessins d'enfants

2015 ◽  
Vol 12 (07) ◽  
pp. 1550067 ◽  
Author(s):  
Michel Planat ◽  
Alain Giorgetti ◽  
Frédéric Holweck ◽  
Metod Saniga
Keyword(s):  
Riemann Surfaces ◽  
Finite Geometries ◽  
Algebraic Numbers ◽  
Distinguished Point ◽  
Magic Square ◽  
Dessins D’Enfants ◽  
Finite Dimensional ◽  
Multipartite Graphs ◽  
Point Line ◽  
Dessins D'enfants

We point out an explicit connection between graphs drawn on compact Riemann surfaces defined over the field [Formula: see text] of algebraic numbers — the so-called Grothendieck's dessins d'enfants — and a wealth of distinguished point-line configurations. These include simplices, cross-polytopes, several notable projective configurations, a number of multipartite graphs and some "exotic" geometries. Among them, remarkably, we find not only those underlying Mermin's magic square and magic pentagram, but also those related to the geometry of two- and three-qubit Pauli groups. Of particular interest is the occurrence of all the three types of slim generalized quadrangles, namely GQ(2, 1), GQ(2, 2) and GQ(2, 4), and a couple of closely related graphs, namely the Schläfli and Clebsch ones. These findings seem to indicate that dessins d'enfants may provide us with a new powerful tool for gaining deeper insight into the nature of finite-dimensional Hilbert spaces and their associated groups, with a special emphasis on contextuality.

scholarly journals 2, 12, 117, 1959, 45171, 1170086, …: a Hilbert series for the QCD chiral Lagrangian

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Lukáš Gráf ◽  
Brian Henning ◽  
Xiaochuan Lu ◽  
Tom Melia ◽  
Hitoshi Murayama
Keyword(s):  
Hilbert Series ◽  
Charge Conjugation ◽  
External Fields ◽  
Dynkin Diagrams ◽  
Non Linear ◽  
Very High ◽  
Chiral Lagrangian

Abstract We apply Hilbert series techniques to the enumeration of operators in the mesonic QCD chiral Lagrangian. Existing Hilbert series technologies for non-linear realizations are extended to incorporate the external fields. The action of charge conjugation is addressed by folding the $$ \mathfrak{su}(n) $$ su n Dynkin diagrams, which we detail in an appendix that can be read separately as it has potential broader applications. New results include the enumeration of anomalous operators appearing in the chiral Lagrangian at order p8, as well as enumeration of CP-even, CP-odd, C-odd, and P-odd terms beginning from order p6. The method is extendable to very high orders, and we present results up to order p16.(The title sequence is the number of independent C-even and P-even operators in the mesonic QCD chiral Lagrangian with three light flavors of quarks, at chiral dimensions p2, p4, p6, …)

An exceptional point switches stability of a thermoacoustic experiment

2021 ◽  
Vol 920 ◽  
Author(s):  
Abdulla Ghani ◽  
Wolfgang Polifke
Keyword(s):  
Exceptional Point

Abstract

scholarly journals Observation of anti-parity-time-symmetry, phase transitions and exceptional points in an optical fibre

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Arik Bergman ◽  
Robert Duggan ◽  
Kavita Sharma ◽  
Moshe Tur ◽  
Avi Zadok ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Brillouin Scattering ◽  
Optical Gain ◽  
Single Mode ◽  
Exceptional Point ◽  
Small Scale ◽  
Time Symmetry ◽  
Topological Features ◽  
Gain And Loss ◽  
Exotic Physics

AbstractThe exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has recently drawn a great deal of attention. These systems exhibit phase transitions and exceptional point singularities in their spectra, at which eigen-values and eigen-modes coalesce and the overall dimensionality is reduced. So far, these principles have been implemented at the expense of precise fabrication and tuning requirements, involving tailored nano-structured devices with controlled optical gain and loss. In this work, anti-parity-time symmetric phase transitions and exceptional point singularities are demonstrated in a single strand of single-mode telecommunication fibre, using a setup consisting of off-the-shelf components. Two propagating signals are amplified and coupled through stimulated Brillouin scattering, enabling exquisite control over the interaction-governing non-Hermitian parameters. Singular response to small-scale variations and topological features arising around the exceptional point are experimentally demonstrated with large precision, enabling robustly enhanced response to changes in Brillouin frequency shift.

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