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BEGIN:VEVENT
SUMMARY:Eric Swartz (William & Mary)
DTSTART:20200416T200000Z
DTEND:20200416T210000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/1
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /1/">Covering numbers of groups</a>\nby Eric Swartz (William & Mary) as pa
 rt of GAG seminar\n\n\nAbstract\nGiven a group $G$\, $G$ can be expressed 
 as the set-theoretical union of proper subgroups as long as $G$ is not cyc
 lic.  \nAssuming $G$ is the union of finitely many proper subgroups\, we d
 efine the covering number of $G$\, denoted by $\\sigma(G)$\, to be the min
 imum number of proper subgroups required in such a union.  \nThis begs the
  question: which integers are covering numbers of finite groups?  This tal
 k will be about joint work with Martino Garonzi and Luise-Charlotte Kappe 
 in our attempts to answer this question\, \nand the material in this talk 
 should be accessible to undergraduate students.\n\nPassword: the order of 
 the alternating group $A_8$.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nick Werner (SUNY Old Westbury)
DTSTART:20200430T200000Z
DTEND:20200430T210000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/2
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /2/">Covering numbers of rings</a>\nby Nick Werner (SUNY Old Westbury) as 
 part of GAG seminar\n\n\nAbstract\nA cover of a ring $R$ is a collection $
 C$ of proper subrings of $R$ such that $R = \\bigcup_{S \\in C} S$. If suc
 h a collection exists\, then $R$ is called coverable\, and the covering nu
 mber of $R$ is the cardinality of the smallest possible cover. Questions t
 hat have been considered on this topic include determining covering number
 s for certain families of rings\, or classifying all rings with a given co
 vering number. As we will demonstrate\, many of these questions can be red
 uced to the case of finite rings of characteristic $p$.\n\nThe analogous p
 roblem of finding covering numbers of groups has been extensively studied.
  While there are parallels between the group setting and the ring setting\
 , much less is known in the case of rings. We will survey the known result
 s on covering numbers of rings\, and mention some conjectures and open pro
 blems\, among them the unresolved question of whether there exists a ring 
 with covering number 13.\n\nPassword to access the talk is the order of th
 e symmetric group $S_9$.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pierre Rousselin (LAGA Paris 13)
DTSTART:20200916T170000Z
DTEND:20200916T180000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/3
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /3/">Conductance of a Subdiffusive Random Weighted Tree</a>\nby Pierre Rou
 sselin (LAGA Paris 13) as part of GAG seminar\n\n\nAbstract\nWe build a ra
 ndom tree with random weights on its edges. These weights are used to defi
 ne a random walk (in a random environment) on the vertices of the tree. \n
 That is a lot of randomness! But do not worry too much\, the tools we use 
 here are mostly analytical (and often elementary). \nAssociated to this ra
 ndom walk is an electrical network formalism: each edge has an electrical 
 conductance (the inverse of its resistance) and we may consider \nthe effe
 ctive conductance between the root of the tree and its $n$-th level. In th
 e regime we are interested in (called "subdiffusive")\, \nthis conductance
  decreases almost surely to $0$ as $n$ goes to infinity and we will try (a
 nd not completely succeed!) to compute an almost sure equivalent of this c
 onductance.\n\nThe password to join the talk is the order of the alternati
 ng group $A_7$.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chi-Kwong Li (William & Mary)
DTSTART:20200923T170000Z
DTEND:20200923T180000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/4
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /4/">Quantum error correction\, operator algebra\, representation theory</
 a>\nby Chi-Kwong Li (William & Mary) as part of GAG seminar\n\n\nAbstract\
 nWe discuss the use of operator algebra techniques and some basic represen
 tation theory in constructing and implementing an quantum error correction
  scheme for the fully  correlated channels  on $n$-qubits with error opera
 tors of the form $W\\otimes \\cdots \\otimes W$\, the Kronecker product of
  $n$ copies of $2\\times 2$ (special)  unitary matrix $W$.\n\nThe password
  to the meeting is the order of the symmetric group $S_7$.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Moritz Weber (Saarland University)
DTSTART:20201028T170000Z
DTEND:20201028T180000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/5
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /5/">Quantum automorphism groups of finite graphs: a survey</a>\nby Moritz
  Weber (Saarland University) as part of GAG seminar\n\n\nAbstract\nBased o
 n the theory of $C^*$-algebras\, Woronowicz developed an analytic approach
  to quantum groups in the 1980s. In the 1990s\, Sh. Wang defined quantum p
 ermutation groups within his framework\; these are quantum versions of the
  well-known symmetric groups. In the 2000s\, Banica and Bichon defined the
  notion of a quantum automorphism group of a finite graph\, building on Wa
 ng’s quantum permutation groups. Such a quantum group contains the autom
 orphism group of the given graph\, but in some cases\, it may be strictly 
 larger. So\, in a way\, we then have more ways of quantum permuting vertic
 es rather than just permuting them - we have more symmetries.\n\nI will br
 iefly introduce to compact matrix quantum groups in the sense of Woronowic
 z and then survey the current knowledge on quantum automorphism groups of 
 graphs. I will also indicate some open problems in this relatively new fie
 ld.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eric Swartz (William & Mary)
DTSTART:20201111T180000Z
DTEND:20201111T190000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/6
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /6/">Coherent configurations and quantum orbital algebras</a>\nby Eric Swa
 rtz (William & Mary) as part of GAG seminar\n\n\nAbstract\nCoherent config
 urations were first introduced by D. Higman in an attempt to "do group the
 ory without groups." We will discuss the definition of coherent configurat
 ions and the related concept of coherent algebras\, and we will show how t
 he theory can be extended to study quantum automorphism groups of graphs.\
 n\nPassword is the order of the symmetric group $S_9$.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Charles Johnson (William & Mary)
DTSTART:20210205T200000Z
DTEND:20210205T210000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/7
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /7/">Topics on the Nonnegative Inverse Eigenvalue Problem</a>\nby Charles 
 Johnson (William & Mary) as part of GAG seminar\n\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Çisil Karagüzel (UC Santa Cruz)
DTSTART:20210423T190000Z
DTEND:20210423T200000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/8
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /8/">Fusion Systems of Blocks of Finite Groups over Arbitrary Fields</a>\n
 by Çisil Karagüzel (UC Santa Cruz) as part of GAG seminar\n\n\nAbstract\
 nGiven a field $k$ of characteristic $p > 0$\, a finite group $G$\, to any
  block idempotent $b$ of the group algebra $kG$\, Puig associated a fusion
  system and proved that it is saturated if the $k$-algebra $kC_G(P)e$ is s
 plit\, where $(P\,e)$ is a maximal $b$-Brauer pair. \nIn this talk\, we wi
 ll investigate in the non-split case how far the fusion system is from bei
 ng saturated by describing it in an explicit way as being generated by the
  fusion system of a related block idempotent over a larger field together 
 with a single automorphism of the defect group.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ethan Shelburne (William & Mary)
DTSTART:20210430T190000Z
DTEND:20210430T200000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/9
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /9/">Toward a Holographic Transform for the Quantum Clebsch-Gordan Formula
 </a>\nby Ethan Shelburne (William & Mary) as part of GAG seminar\n\n\nAbst
 ract\nA holographic transform is an equivariant map which increases the nu
 mber of variables in its domain\, a space of functions. The tensor product
  of two finite dimensional irreducible representations of the Lie algebra 
 $\\mathfrak{sl}(2)$ decomposes into a direct sum of irreducible modules. I
 n fact\, the tensor product of representations of $U_q(\\mathfrak{sl}(2))$
 \, the quantum analogue of $\\mathfrak{sl}(2)$\, decomposes in the same wa
 y. The purpose of this talk will be discussing the search for explicit hol
 ographic transforms associated with these decompositions.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gexin Yu (William & Mary)
DTSTART:20210908T180000Z
DTEND:20210908T190000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/10
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /10/">Sufficient conditions for 2-dimensional graph rigidity</a>\nby Gexin
  Yu (William & Mary) as part of GAG seminar\n\nLecture held in Jones Hall 
 302.\nAbstract: TBA\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cordelia Li (William & Mary)
DTSTART:20210929T180000Z
DTEND:20210929T190000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/11
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /11/">Copositive matrices\, their dual\, and the Recognition Problem</a>\n
 by Cordelia Li (William & Mary) as part of GAG seminar\n\nLecture held in 
 Jones Hall 302.\n\nAbstract\nCopositivity is a generalization of positive 
 semidefiniteness.  It has applications in economics\, operations research\
 , and statistics.\nAn $n$-by-$n$ real matrix $A$ is copositive (CoP) if $x
 ^TAx \\ge 0$ for any nonnegative vector $x \\ge 0$.  The CoP matrices form
  a proper cone.\nA CoP matrix is ordinary if it can be written as the sum 
 of a positive semidefinite (PSD) matrix and a symmetric nonnegative (sN) m
 atrix.\nWhen $n < 5$\, all copositive matrices are ordinary.  However\, re
 cognition that a given CoP matrix is ordinary and the determination of an 
 ordinary decomposition is an unresolved issue.\nHere\, we make observation
 s about CoP-preserving operations\, make progress about the recognition pr
 oblem\, and discuss the relationship between the recognition problem and t
 he PSD completion problem.\nWe also mention the problem of copositive spec
 tra and its relation to the symmetric nonnegative inverse eigenvalue probl
 em.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gabriel Martins (Sacramento State)
DTSTART:20211006T180000Z
DTEND:20211006T190000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/12
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /12/">Skateboard tricks and topological flips</a>\nby Gabriel Martins (Sac
 ramento State) as part of GAG seminar\n\nLecture held in Jones Hall 302.\n
 \nAbstract\nWe study the motion of skateboard flip tricks by modeling them
  as continuous curves in the group  $\\mathrm{SO}(3)$ of special orthogona
 l matrices. We show that up to continuous deformation there are only four 
 flip tricks. The proof relies on an analysis of the lift of such curves to
  the unit-sphere. We are also able to use these lifted curves to visualize
  many of the tricks and deformations between them.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eric Swartz (William & Mary)
DTSTART:20211020T180000Z
DTEND:20211020T190000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/13
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /13/">Covering numbers of rings with unity</a>\nby Eric Swartz (William & 
 Mary) as part of GAG seminar\n\nLecture held in Jones Hall 302.\n\nAbstrac
 t\nGiven an algebraic structure (group\, ring\, etc.)\, a cover is defined
  to be a collection of proper substructures (e.g.\, subgroups\, subrings\,
  etc.) whose set theoretic union is the whole structure.  Assuming such an
  algebraic structure has a cover\, its covering number is defined to be th
 e size of a minimum cover.  I will discuss the rich history of this proble
 m as well as recent joint work with Nicholas Werner on the covering number
  of a ring with unity.  No prior knowledge will be assumed beyond the basi
 c definitions of groups and rings.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sage Stanish (William & Mary)
DTSTART:20211201T190000Z
DTEND:20211201T200000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/14
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /14/">An application of Computational Homology to the Ising Model</a>\nby 
 Sage Stanish (William & Mary) as part of GAG seminar\n\nLecture held in Jo
 nes Hall 302.\n\nAbstract\nHomology groups were developed in algebraic top
 ology as a way of distinguishing objects by counting their holes.  Recentl
 y\, computers and algorithms have improved to the point where it is effici
 ent to compute the homology of arbitrary data.  This is being used in a wi
 de variety of applications to study real world systems.  Here\, we develop
  the basic theory of homology on cubical sets.  We then look at an applica
 tion of this tool in studying the Ising model.  We assume no prior knowled
 ge beyond basic group theory.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dan Cranston (VCU)
DTSTART:20220221T203000Z
DTEND:20220221T213000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/15
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /15/">In most 6-regular toroidal graphs All 5-colorings are Kempe equivale
 nt</a>\nby Dan Cranston (VCU) as part of GAG seminar\n\nLecture held in Bo
 swell Hall 203.\n\nAbstract\nA Kempe swap in a proper coloring interchange
 s the colors on some\nmaximal connected 2-colored subgraph. Two $k$-colori
 ngs are $k$-equivalent\nif we can transform one into the other using Kempe
  swaps. We show that\nif $G$ is 6-regular with a toroidal embedding where 
 every\nnon-contractible cycle has length at least 7\, then all 5-colorings
  of\n$G$ are 5-equivalent. Bonamy\, Bousquet\, Feghali\, and Johnson asked
  if\nthis holds when $G$ is formed from the Cartesian product of $C_m$ and
  $C_n$\nby adding parallel diagonals inside all 4-faces (this graph is of 
 interest in\nstatistical mechanics). We answer their question affirmativel
 y when\n$m\,n \\geq 6$.  This is joint work with Reem Mahmoud.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Edward Poon (ERAU)
DTSTART:20220322T180000Z
DTEND:20220322T190000Z
DTSTAMP:20260404T094913Z
UID:WMGAG/16
DESCRIPTION:Title: <a href="https://stable.researchseminars.org/talk/WMGAG
 /16/">Matrices with circular higher rank numerical range</a>\nby Edward Po
 on (ERAU) as part of GAG seminar\n\nLecture held in Boswell Hall 203.\n\nA
 bstract\nThe rank-$k$ numerical range of a square matrix $A$ is the set of
  all complex numbers $c$ such that $PAP = cP$ for some rank-$k$ orthogonal
  projection $P$. (When $k=1$\, this reduces to the classical numerical ran
 ge.)  We investigate conditions on when the rank-k numerical range is a ci
 rcular disk. \n This talk is based on joint work with Ilya Spitkovsky and 
 Hugo Woerdeman.\n
LOCATION:https://stable.researchseminars.org/talk/WMGAG/16/
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