BEGIN:VCALENDAR
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CALSCALE:GREGORIAN
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BEGIN:VEVENT
SUMMARY:Eric Swartz (William & Mary)
DTSTART:20200416T200000Z
DTEND:20200416T210000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/1
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/1/">Co
 vering numbers of groups</a>\nby Eric Swartz (William & Mary) as part of G
 AG 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 cyclic.  \
 nAssuming $G$ is the union of finitely many proper subgroups\, we define t
 he covering number of $G$\, denoted by $\\sigma(G)$\, to be the minimum nu
 mber of proper subgroups required in such a union.  \nThis begs the questi
 on: which integers are covering numbers of finite groups?  This talk 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 alt
 ernating group $A_8$.\n
LOCATION:https://researchseminars.org/talk/WMGAG/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Nick Werner (SUNY Old Westbury)
DTSTART:20200430T200000Z
DTEND:20200430T210000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/2
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/2/">Co
 vering 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 p
 roper subrings of $R$ such that $R = \\bigcup_{S \\in C} S$. If such a col
 lection exists\, then $R$ is called coverable\, and the covering number of
  $R$ is the cardinality of the smallest possible cover. Questions that hav
 e been considered on this topic include determining covering numbers for c
 ertain families of rings\, or classifying all rings with a given covering 
 number. As we will demonstrate\, many of these questions can be reduced to
  the case of finite rings of characteristic $p$.\n\nThe analogous problem 
 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 results on co
 vering numbers of rings\, and mention some conjectures and open problems\,
  among them the unresolved question of whether there exists a ring with co
 vering number 13.\n\nPassword to access the talk is the order of the symme
 tric group $S_9$.\n
LOCATION:https://researchseminars.org/talk/WMGAG/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Pierre Rousselin (LAGA Paris 13)
DTSTART:20200916T170000Z
DTEND:20200916T180000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/3
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/3/">Co
 nductance of a Subdiffusive Random Weighted Tree</a>\nby Pierre Rousselin 
 (LAGA Paris 13) as part of GAG seminar\n\n\nAbstract\nWe build a random tr
 ee with random weights on its edges. These weights are used to define a ra
 ndom walk (in a random environment) on the vertices of the tree. \nThat is
  a lot of randomness! But do not worry too much\, the tools we use here ar
 e mostly analytical (and often elementary). \nAssociated to this random wa
 lk is an electrical network formalism: each edge has an electrical conduct
 ance (the inverse of its resistance) and we may consider \nthe effective c
 onductance between the root of the tree and its $n$-th level. In the regim
 e we are interested in (called "subdiffusive")\, \nthis conductance decrea
 ses almost surely to $0$ as $n$ goes to infinity and we will try (and not 
 completely succeed!) to compute an almost sure equivalent of this conducta
 nce.\n\nThe password to join the talk is the order of the alternating grou
 p $A_7$.\n
LOCATION:https://researchseminars.org/talk/WMGAG/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Chi-Kwong Li (William & Mary)
DTSTART:20200923T170000Z
DTEND:20200923T180000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/4
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/4/">Qu
 antum error correction\, operator algebra\, representation theory</a>\nby 
 Chi-Kwong Li (William & Mary) as part of GAG seminar\n\n\nAbstract\nWe dis
 cuss the use of operator algebra techniques and some basic representation 
 theory in constructing and implementing an quantum error correction scheme
  for the fully  correlated channels  on $n$-qubits with error operators of
  the form $W\\otimes \\cdots \\otimes W$\, the Kronecker product of $n$ co
 pies 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://researchseminars.org/talk/WMGAG/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Moritz Weber (Saarland University)
DTSTART:20201028T170000Z
DTEND:20201028T180000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/5
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/5/">Qu
 antum automorphism groups of finite graphs: a survey</a>\nby Moritz Weber 
 (Saarland University) as part of GAG seminar\n\n\nAbstract\nBased on the t
 heory of $C^*$-algebras\, Woronowicz developed an analytic approach to qua
 ntum groups in the 1980s. In the 1990s\, Sh. Wang defined quantum permutat
 ion groups within his framework\; these are quantum versions of the well-k
 nown symmetric groups. In the 2000s\, Banica and Bichon defined the notion
  of a quantum automorphism group of a finite graph\, building on Wang’s 
 quantum permutation groups. Such a quantum group contains the automorphism
  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 vertices rath
 er than just permuting them - we have more symmetries.\n\nI will briefly i
 ntroduce to compact matrix quantum groups in the sense of Woronowicz and t
 hen survey the current knowledge on quantum automorphism groups of graphs.
  I will also indicate some open problems in this relatively new field.\n
LOCATION:https://researchseminars.org/talk/WMGAG/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eric Swartz (William & Mary)
DTSTART:20201111T180000Z
DTEND:20201111T190000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/6
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/6/">Co
 herent configurations and quantum orbital algebras</a>\nby Eric Swartz (Wi
 lliam & Mary) as part of GAG seminar\n\n\nAbstract\nCoherent configuration
 s were first introduced by D. Higman in an attempt to "do group theory wit
 hout groups." We will discuss the definition of coherent configurations an
 d the related concept of coherent algebras\, and we will show how the theo
 ry can be extended to study quantum automorphism groups of graphs.\n\nPass
 word is the order of the symmetric group $S_9$.\n
LOCATION:https://researchseminars.org/talk/WMGAG/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Charles Johnson (William & Mary)
DTSTART:20210205T200000Z
DTEND:20210205T210000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/7
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/7/">To
 pics on the Nonnegative Inverse Eigenvalue Problem</a>\nby Charles Johnson
  (William & Mary) as part of GAG seminar\n\nAbstract: TBA\n
LOCATION:https://researchseminars.org/talk/WMGAG/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Çisil Karagüzel (UC Santa Cruz)
DTSTART:20210423T190000Z
DTEND:20210423T200000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/8
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/8/">Fu
 sion Systems of Blocks of Finite Groups over Arbitrary Fields</a>\nby Çis
 il 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 split\, 
 where $(P\,e)$ is a maximal $b$-Brauer pair. \nIn this talk\, we will inve
 stigate in the non-split case how far the fusion system is from being satu
 rated 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://researchseminars.org/talk/WMGAG/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Ethan Shelburne (William & Mary)
DTSTART:20210430T190000Z
DTEND:20210430T200000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/9
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/9/">To
 ward a Holographic Transform for the Quantum Clebsch-Gordan Formula</a>\nb
 y Ethan Shelburne (William & Mary) as part of GAG seminar\n\n\nAbstract\nA
  holographic transform is an equivariant map which increases the number of
  variables in its domain\, a space of functions. The tensor product of two
  finite dimensional irreducible representations of the Lie algebra $\\math
 frak{sl}(2)$ decomposes into a direct sum of irreducible modules. In fact\
 , the tensor product of representations of $U_q(\\mathfrak{sl}(2))$\, the 
 quantum analogue of $\\mathfrak{sl}(2)$\, decomposes in the same way. The 
 purpose of this talk will be discussing the search for explicit holographi
 c transforms associated with these decompositions.\n
LOCATION:https://researchseminars.org/talk/WMGAG/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gexin Yu (William & Mary)
DTSTART:20210908T180000Z
DTEND:20210908T190000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/10
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/10/">S
 ufficient conditions for 2-dimensional graph rigidity</a>\nby Gexin Yu (Wi
 lliam & Mary) as part of GAG seminar\n\nLecture held in Jones Hall 302.\nA
 bstract: TBA\n
LOCATION:https://researchseminars.org/talk/WMGAG/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Cordelia Li (William & Mary)
DTSTART:20210929T180000Z
DTEND:20210929T190000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/11
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/11/">C
 opositive matrices\, their dual\, and the Recognition Problem</a>\nby Cord
 elia Li (William & Mary) as part of GAG seminar\n\nLecture held in Jones H
 all 302.\n\nAbstract\nCopositivity is a generalization of positive semidef
 initeness.  It has applications in economics\, operations research\, and s
 tatistics.\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 prop
 er cone.\nA CoP matrix is ordinary if it can be written as the sum of a po
 sitive semidefinite (PSD) matrix and a symmetric nonnegative (sN) matrix.\
 nWhen $n < 5$\, all copositive matrices are ordinary.  However\, recogniti
 on that a given CoP matrix is ordinary and the determination of an ordinar
 y decomposition is an unresolved issue.\nHere\, we make observations about
  CoP-preserving operations\, make progress about the recognition problem\,
  and discuss the relationship between the recognition problem and the PSD 
 completion problem.\nWe also mention the problem of copositive spectra and
  its relation to the symmetric nonnegative inverse eigenvalue problem.\n
LOCATION:https://researchseminars.org/talk/WMGAG/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Gabriel Martins (Sacramento State)
DTSTART:20211006T180000Z
DTEND:20211006T190000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/12
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/12/">S
 kateboard tricks and topological flips</a>\nby Gabriel Martins (Sacramento
  State) as part of GAG seminar\n\nLecture held in Jones Hall 302.\n\nAbstr
 act\nWe study the motion of skateboard flip tricks by modeling them as con
 tinuous curves in the group  $\\mathrm{SO}(3)$ of special orthogonal matri
 ces. We show that up to continuous deformation there are only four flip tr
 icks. The proof relies on an analysis of the lift of such curves to the un
 it-sphere. We are also able to use these lifted curves to visualize many o
 f the tricks and deformations between them.\n
LOCATION:https://researchseminars.org/talk/WMGAG/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Eric Swartz (William & Mary)
DTSTART:20211020T180000Z
DTEND:20211020T190000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/13
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/13/">C
 overing numbers of rings with unity</a>\nby Eric Swartz (William & Mary) a
 s part of GAG seminar\n\nLecture held in Jones Hall 302.\n\nAbstract\nGive
 n 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 algebr
 aic structure has a cover\, its covering number is defined to be the size 
 of a minimum cover.  I will discuss the rich history of this problem as we
 ll as recent joint work with Nicholas Werner on the covering number of a r
 ing with unity.  No prior knowledge will be assumed beyond the basic defin
 itions of groups and rings.\n
LOCATION:https://researchseminars.org/talk/WMGAG/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Sage Stanish (William & Mary)
DTSTART:20211201T190000Z
DTEND:20211201T200000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/14
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/14/">A
 n application of Computational Homology to the Ising Model</a>\nby Sage St
 anish (William & Mary) as part of GAG seminar\n\nLecture held in Jones Hal
 l 302.\n\nAbstract\nHomology groups were developed in algebraic topology a
 s a way of distinguishing objects by counting their holes.  Recently\, com
 puters and algorithms have improved to the point where it is efficient to 
 compute the homology of arbitrary data.  This is being used in a wide vari
 ety of applications to study real world systems.  Here\, we develop the ba
 sic theory of homology on cubical sets.  We then look at an application of
  this tool in studying the Ising model.  We assume no prior knowledge beyo
 nd basic group theory.\n
LOCATION:https://researchseminars.org/talk/WMGAG/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dan Cranston (VCU)
DTSTART:20220221T203000Z
DTEND:20220221T213000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/15
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/15/">I
 n most 6-regular toroidal graphs All 5-colorings are Kempe equivalent</a>\
 nby Dan Cranston (VCU) as part of GAG seminar\n\nLecture held in Boswell H
 all 203.\n\nAbstract\nA Kempe swap in a proper coloring interchanges the c
 olors on some\nmaximal connected 2-colored subgraph. Two $k$-colorings 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\n
 non-contractible cycle has length at least 7\, then all 5-colorings of\n$G
 $ are 5-equivalent. Bonamy\, Bousquet\, Feghali\, and Johnson asked if\nth
 is 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 interes
 t in\nstatistical mechanics). We answer their question affirmatively when\
 n$m\,n \\geq 6$.  This is joint work with Reem Mahmoud.\n
LOCATION:https://researchseminars.org/talk/WMGAG/15/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Edward Poon (ERAU)
DTSTART:20220322T180000Z
DTEND:20220322T190000Z
DTSTAMP:20260422T225818Z
UID:WMGAG/16
DESCRIPTION:Title: <a href="https://researchseminars.org/talk/WMGAG/16/">M
 atrices with circular higher rank numerical range</a>\nby Edward Poon (ERA
 U) as part of GAG seminar\n\nLecture held in Boswell Hall 203.\n\nAbstract
 \nThe rank-$k$ numerical range of a square matrix $A$ is the set of all co
 mplex numbers $c$ such that $PAP = cP$ for some rank-$k$ orthogonal projec
 tion $P$. (When $k=1$\, this reduces to the classical numerical range.)  W
 e investigate conditions on when the rank-k numerical range is a circular 
 disk. \n This talk is based on joint work with Ilya Spitkovsky and Hugo Wo
 erdeman.\n
LOCATION:https://researchseminars.org/talk/WMGAG/16/
END:VEVENT
END:VCALENDAR