BEGIN:VCALENDAR
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CALSCALE:GREGORIAN
X-WR-CALNAME:researchseminars.org
BEGIN:VEVENT
SUMMARY:Ruochuan Liu (Peking University)
DTSTART;VALUE=DATE-TIME:20201023T101500Z
DTEND;VALUE=DATE-TIME:20201023T111500Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/1
DESCRIPTION:Title: Topological cyclic homology for p-adic local fields\nb
y Ruochuan Liu (Peking University) as part of Beijing Moscow Mathematics C
olloquium\n\n\nAbstract\nWe introduce a new approach to compute topologica
l cyclic homology using the descent spectral sequence and the algebraic Ta
te spectral sequence. We carry out computations in the case of a $p$-adic
local field with coefficient ${\\mathbb F}_p$. Joint work with Guozhen Wan
g.\n\nMeeting ID: 648 6454 8936 Password: 899678\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/1/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Dmitry Frolenkov (Steklov Mathematical Institute of RAS)
DTSTART;VALUE=DATE-TIME:20201023T111500Z
DTEND;VALUE=DATE-TIME:20201023T121500Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/2
DESCRIPTION:Title: Additive divisor problem and Applications\nby Dmitry F
rolenkov (Steklov Mathematical Institute of RAS) as part of Beijing Moscow
Mathematics Colloquium\n\n\nAbstract\nAdditive Divisor Problem (ADP) is c
oncerned with finding an asymptotic formula for the sum $\\sum_{n< X}d(n)d
(n+a)$\, where $d(n)=\\sum_{d|n}1$ is the divisor function. Surprisingly\,
the ADP arises naturally in quite different problems of number theory. Fo
r example\, it is related to the investigation of the 4th moment of the Ri
emann zeta-function\, the second moment of automorphic L-functions and the
mean values of the length of continued fractions. In the talk\, I will de
scribe the ADP and its applications.\n\nMeeting ID：648 6454 8936 Passwor
d：899678\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/2/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yi Shi (Peking University)
DTSTART;VALUE=DATE-TIME:20201106T080000Z
DTEND;VALUE=DATE-TIME:20201106T090000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/3
DESCRIPTION:Title: Spectrum rigidity and integrability for Anosov diffeomorph
isms\nby Yi Shi (Peking University) as part of Beijing Moscow Mathemat
ics Colloquium\n\n\nAbstract\nLet $f$ be a partially hyperbolic derived-fr
om-Anosov diffeomorphism on 3-torus $\\mathbb{T}^3$. We show that the stab
le and unstable bundle of $f$ is jointly integrable if and only if $f$ is
Anosov and admits spectrum rigidity in the center bundle. This proves the
Ergodic Conjecture on $\\mathbb{T}^3$.\n\nIn higher dimensions\, let $A\\i
n{\\rm SL}(n\,\\mathbb{Z})$ be an irreducible hyperbolic matrix admitting
complex simple spectrum with different moduli\, then $A$ induces a diffeom
orphism on $\\mathbb{T}^n$. We will also discuss the equivalence of integr
ability and spectrum rigidity for $f\\in{\\rm Diff}^2(\\mathbb{T}^n)$ whic
h is $C^1$-close to $A$.\n\nZoom Meeting ID: 674 4141 7410\nPassword: 9051
98\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/3/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Lev Lokutsievskiy (Steklov Mathematical Institute of RAS)
DTSTART;VALUE=DATE-TIME:20201106T090000Z
DTEND;VALUE=DATE-TIME:20201106T100000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/4
DESCRIPTION:Title: Аn application of algebraic topology and graph theory in
microeconomics\nby Lev Lokutsievskiy (Steklov Mathematical Institute o
f RAS) as part of Beijing Moscow Mathematics Colloquium\n\n\nAbstract\nOne
of the important questions in mechanism design is the implementability of
allocation rules. An allocation rule is called implementable if for any a
gent\, benefit from revealing its true type is better than benefit from ly
ing. I’ll show some illustrative examples. Obviously\, some allocation r
ules are not implementable. Rochet’s theorem states that an allocation r
ule is implementable iff it is cyclically monotone. During the talk\, I’
ll present a new convenient topological condition that guarantees that cyc
lic monotonicity is equivalent to ordinary monotonicity. The last one is e
asy to check (in contrary to cyclic one). Graph theory and algebraic topol
ogy appear to be very useful here.\n\nZoom Meeting ID: 674 4141 7410 \nPas
sword: 905198\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/4/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Taras Panov (Moscow State University)
DTSTART;VALUE=DATE-TIME:20201120T080000Z
DTEND;VALUE=DATE-TIME:20201120T090000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/5
DESCRIPTION:Title: Right-angled polytopes\, hyperbolic manifolds and torus ac
tions\nby Taras Panov (Moscow State University) as part of Beijing Mos
cow Mathematics Colloquium\n\n\nAbstract\nA combinatorial 3-dimensional po
lytope $P$ can be realized in Lobachevsky 3-space with right dihedral angl
es if and only if it is simple\, flag and does not have 4-belts of facets.
This criterion was proved in the works of A. Pogorelov and E. Andreev of
the 1960s. We refer to combinatorial 3 polytopes admitting a right-angled
realisation in Lobachevsky 3-space as Pogorelov polytopes. The Pogorelov c
lass contains all fullerenes\, i.e. simple 3-polytopes with only 5-gonal a
nd 6-gonal facets. There are two families of smooth manifolds associated w
ith Pogorelov polytopes. The first family consists of 3-dimensional small
covers (in the sense of M. Davis and T. Januszkiewicz) of Pogorelov polyto
pes $P$\, also known as hyperbolic 3-manifolds of Loebell type. These are
aspherical 3-manifolds whose fundamental groups are certain extensions of
abelian 2-groups by hyperbolic right-angled reflection groups in the facet
s of $P$. The second family consists of 6-dimensional quasi toric manifold
s over Pogorelov polytopes. These are simply connected 6-manifolds with a
3-dimensional torus action and orbit space $P$. Our main result is that bo
th families are cohomologically rigid\, i.e. two manifolds $M$ and $M'$ fr
om either family are diffeomorphic if and only if their cohomology rings a
re isomorphic. We also prove that a cohomology ring isomorphism implies an
equivalence of characteristic pairs\; in particular\, the corresponding p
olytopes $P$ and $P'$ are combinatorially equivalent. This leads to a posi
tive solution of a problem of A. Vesnin (1991) on hyperbolic Loebell manif
olds\, and implies their full classification. Our results are intertwined
with classical subjects of geometry and topology such as combinatorics of
3-polytopes\, the Four Colour Theorem\, aspherical manifolds\, a diffeomor
phism classification of 6-manifolds and invariance of Pontryagin classes.
The proofs use techniques of toric topology. This is a joint work with V.
Buchstaber\, N. Erokhovets\, M. Masuda and S. Park.\n\nZoom Meeting ID: 62
6 6992 6224 Password: 363601\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/5/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Yi Liu (Beijing International Center for Mathematical Research)
DTSTART;VALUE=DATE-TIME:20201120T090000Z
DTEND;VALUE=DATE-TIME:20201120T100000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/6
DESCRIPTION:Title: Finite covers of 3-manifolds\nby Yi Liu (Beijing Inter
national Center for Mathematical Research) as part of Beijing Moscow Mathe
matics Colloquium\n\n\nAbstract\nIn this talk\, I will discuss some develo
pments in 3-manifold topology of this century regarding finite covering sp
aces. These developments led to the resolution of Thurston's virtual Haken
conjecture and other related conjectures around 2012. Since then\, people
have been seeking for new applications of those techniques and their comb
ination with other branches of mathematics.\n\nZoom Meeting ID: 626 6992 6
224 Password: 363601\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/6/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Alexander Gaifullin (Steklov Mathematical Institute of RAS)
DTSTART;VALUE=DATE-TIME:20201204T080000Z
DTEND;VALUE=DATE-TIME:20201204T090000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/7
DESCRIPTION:Title: On homology of Torelli groups\nby Alexander Gaifullin
(Steklov Mathematical Institute of RAS) as part of Beijing Moscow Mathemat
ics Colloquium\n\n\nAbstract\nThe mapping class groups of oriented surface
s are important examples of groups whose properties are closely related to
geometry and topology of moduli spaces\, topology of 3-manifolds\, automo
rphisms of free groups. The mapping class group of a closed oriented surfa
ce contains two important subgroups\, the Torelli group\, which consists o
f all mapping classes that act trivially on the homology of the surface\,
and the Johnson kernel\, which is the subgroup generated by all Dehn twist
s about separating curves. The talk will be devoted to results on homology
of these two subgroups. Namely\, we will show that the $k$-dimensional ho
mology group of the genus g Torelli group is not finitely generated\, prov
ided that k is in range from $2g-3$ and $3g-5$ (the case $3g-5$ was previo
usly known by a result of Bestvina\, Bux\, and Margalit)\, and the $(2g-3)
$-dimensional homology group the genus g Johnson kernel is also not finite
ly generated. The proof is based on a detailed study of the spectral seque
nces associated with the actions of these groups on the complex of cycles
constructed by Bestvina\, Bux\, and Margalit.\n\nZoom Meeting ID: 668 8175
3105\nPassword: 348558\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/7/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Guozhen Wang (Shanghai Center for Mathematical Sciences\, Fudan Un
iversity)
DTSTART;VALUE=DATE-TIME:20201204T090000Z
DTEND;VALUE=DATE-TIME:20201204T100000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/8
DESCRIPTION:Title: Stable homotopy groups of spheres\nby Guozhen Wang (Sh
anghai Center for Mathematical Sciences\, Fudan University) as part of Bei
jing Moscow Mathematics Colloquium\n\n\nAbstract\nWe will discuss the curr
ent state of knowledge of stable homotopy groups of spheres. We describe a
computational method using motivic homotopy theory\, viewed as a deformat
ion of classical homotopy theory. This yields a streamlined computation of
the first 61 stable homotopy groups and gives information about the stabl
e homotopy groups in dimensions 62 through 90. As an application\, we dete
rmine the groups of homotopy spheres that classify smooth structures on sp
heres through dimension 90\, except for dimension 4. The method relies mor
e heavily on machine computations than previous methods and is therefore l
ess prone to error. The main mathematical tool is the Adams spectral seque
nce.\n\nZoom Meeting ID: 668 8175 3105 Password: 348558\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/8/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Zhifei Zhang (School of Mathematical Sciences\, Peking University)
DTSTART;VALUE=DATE-TIME:20210115T080000Z
DTEND;VALUE=DATE-TIME:20210115T090000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/9
DESCRIPTION:Title: Linear stability of pipe Poiseuille flow at high Reynolds
number regime\nby Zhifei Zhang (School of Mathematical Sciences\, Peki
ng University) as part of Beijing Moscow Mathematics Colloquium\n\n\nAbstr
act\nThe linear stability of pipe Poiseuille flow is a long standing probl
em since Reynolds experiment in 1883. Joint with Qi Chen and Dongyi Wei\,
we solve this problem at high Reynolds regime. We first introduce a new fo
rmulation for the linearized 3-D Navier-Stokes equations around this flow.
Then we establish the resolvent estimates of this new system under favora
ble artificial boundary conditions. Finally\, we solve the original system
by constructing a boundary layer corrector.\n\nMeeting ID：645 2363 5960
\nPassword：714716\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/9/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Vladimir E. Nazaikinskii (Ishlinsky Institute for Problems in Mech
anics RAS)
DTSTART;VALUE=DATE-TIME:20210115T090000Z
DTEND;VALUE=DATE-TIME:20210115T100000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/10
DESCRIPTION:Title: Partial spectral flow and the Aharonov-Bohm effect in gra
phene\nby Vladimir E. Nazaikinskii (Ishlinsky Institute for Problems i
n Mechanics RAS) as part of Beijing Moscow Mathematics Colloquium\n\n\nAbs
tract\nWe study the Aharonov-Bohm effect in an open-ended tube made of a g
raphene sheet whose dimensions are much larger than the interatomic distan
ce in graphene. An external magnetic field vanishes on and in the vicinity
of the graphene sheet\, and its flux through the tube is adiabatically sw
itched on. It is shown that\, in the process\, the energy levels of the ti
ght-binding Hamiltonian of $\\pi$-electrons unavoidably cross the Fermi le
vel\, which results in the creation of electron-hole pairs. The number of
pairs is proven to be equal to the number of magnetic flux quanta of the e
xternal field. The proof is based on the new notion of partial spectral fl
ow\, which generalizes the ordinary spectral flow introduced by Atiyah\, P
atodi\, and Singer and already having well-known applications (such as the
Kopnin forces in superconductors and superfluids) in condensed matter phy
sics.\n\nMeeting ID：645 2363 5960\nPassword：714716\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/10/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Armen Sergeev (Steklov Mathematical Institute of RAS)
DTSTART;VALUE=DATE-TIME:20210312T080000Z
DTEND;VALUE=DATE-TIME:20210312T090000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/11
DESCRIPTION:Title: Mathematical problems in the theory of topological insula
tors\nby Armen Sergeev (Steklov Mathematical Institute of RAS) as part
of Beijing Moscow Mathematics Colloquium\n\n\nAbstract\nThe talk is devot
ed to the theory of topological insulators - a new and actively developing
direction in solid state physics. To find a new topological object one ha
ve to look for the appropiate topological invariants and systems for which
these invariants are non-trivial. The topological insulators are characte
rized by having wide energy gap stable for small deformations. A nice exam
ple is given by the quantum Hall spin insulator. It is a two-dimensional i
nsulator invariant under the time reversal. It is characterized by the non
-trivial topological $\\mathbb Z_2$-invariant introduced by Kane and Mele.
\nIn our talk we consider the topological insulators invariant under time
reversal. In the first part we present the physical basics of their theory
while the second part deals with the mathematical aspects. These aspects
are closely related to K-theory and non-commutative geometry.\n\nZoom Meet
ing ID: 646 2331 6558\nPassword：574262\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/11/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Oleg German (Moscow State University)
DTSTART;VALUE=DATE-TIME:20210326T080000Z
DTEND;VALUE=DATE-TIME:20210326T090000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/12
DESCRIPTION:Title: Transference principle in Diophantine approximation\n
by Oleg German (Moscow State University) as part of Beijing Moscow Mathema
tics Colloquium\n\n\nAbstract\nThe talk will be devoted to one of the fund
amental principles in Diophantine approximation called transference princi
ple. It reflects the relation of duality between certain problems. This pr
inciple is usually formulated in terms of Diophantine exponents - they gen
eralise to the multidimensional case the measure of irrationality of a rea
l number. We plan to give an account on the existing relations Diophantine
exponents satisfy and try to reveal the geometric nature of those relatio
ns. After having described some basic geometric constructions\, we shall l
ook from this perspective at the famous linear independence criterion that
belongs to Nesterenko. It appears that our approach provides an alternati
ve proof of this criterion\, which bases on rather simple geometric consid
erations.\n\nZoom Meeting ID: 673 7981 0561\nPassword：263867\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/12/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Hu Yongquan (Morningside Center of Mathematics\, Academy of Mathem
atics and Systems Science)
DTSTART;VALUE=DATE-TIME:20210326T090000Z
DTEND;VALUE=DATE-TIME:20210326T100000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/13
DESCRIPTION:Title: Introduction to p-adic Langlands program for GL_2\nby
Hu Yongquan (Morningside Center of Mathematics\, Academy of Mathematics a
nd Systems Science) as part of Beijing Moscow Mathematics Colloquium\n\n\n
Abstract\nThe $p$-adic and mod $p$ Langlands program is an avatar of the c
lassical Langlands program and has been first initiated by C. Breuil. In t
his colloquium talk\, I will give a brief introduction to the program and
survey some recent progress in the case of $GL_2$.\n\nMeeting ID: 673 7981
0561\nPassword：263867\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/13/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Anton Trushechkin (Steklov Mathematical Institute of RAS)
DTSTART;VALUE=DATE-TIME:20210409T080000Z
DTEND;VALUE=DATE-TIME:20210409T090000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/14
DESCRIPTION:Title: Mathematical methods of quantum key distribution\nby
Anton Trushechkin (Steklov Mathematical Institute of RAS) as part of Beiji
ng Moscow Mathematics Colloquium\n\n\nAbstract\nQuantum key distribution a
nd\, more generally\, quantum cryptography is a modern branch of science w
here methods of secure communication based on principles of quantum mechan
ics are studied. The rigorous proof of the security of quantum key distrib
ution gave rise to a complex and beautiful mathematical theory\, which is
based on methods of quantum information theory\, namely\, quantum entropi
c measures and entropic uncertainty relations. In particular\, to estimate
secret key rate\, one needs to minimize the quantum relative entropy (a c
onvex function) subject to linear constraints. The problem is\, in general
\, infinite-dimensional\, but symmetry properties of the problem reduces t
he dimensionality and allows one to solve this problem analytically. Howev
er\, currently\, an important task is to prove the security of quantum key
distribution with imperfect (i.e.\, practical) devices. Imperfections int
roduce asymmetries and thus make the problem more complicated. In the talk
\, estimations for the secret key rate in the case of detection-efficiency
mismatch will be presented. Using entropic uncertainty relations\, an inf
inite-dimensional problem is reduced to a one-dimensional one.\n\nMeeting
ID:633 6361 1209\nPassword: 127853\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/14/
END:VEVENT
BEGIN:VEVENT
SUMMARY:Feihu Xu (University of Science and Technology of China)
DTSTART;VALUE=DATE-TIME:20210409T090000Z
DTEND;VALUE=DATE-TIME:20210409T100000Z
DTSTAMP;VALUE=DATE-TIME:20210418T110506Z
UID:BeijingMoscowColloquium/15
DESCRIPTION:Title: A quantum leap in security\nby Feihu Xu (University o
f Science and Technology of China) as part of Beijing Moscow Mathematics C
olloquium\n\n\nAbstract\nQuantum cryptography or quantum key distribution
(QKD) offers information-theoretic security based on the laws of physics.
This is the technology at the basis of the quantum satellite "Mozi"\, put
in orbit by the Chinese Academy of Sciences in 2016. In practice\, however
\, the imperfections of realistic devices might introduce deviations from
the idealized models used in the security proofs of QKD. Can quantum code
breakers successfully hack real systems by exploiting the side channels? C
an quantum code makers design innovative countermeasures to foil quantum c
ode breakers? In this talk\, I will talk about the theoretical and experim
ental progress in the practical security aspects of quantum code making an
d quantum code breaking. After numerous attempts over the past decades\, r
esearchers now thoroughly understand and are able to manage the practical
imperfections. Recent advances\, such as the decoy-state\, measurement-dev
ice-independent (MDI) and twin-field (TF) protocols\, have closed critical
side channels in the physical implementations in a rigorous and practical
manner. Further readings in [Xu et al.\, Rev. Mod. Phys. 92\, 025002 (202
0)].\n\nMeeting ID: 633 6361 1209\nPassword: 127853\n
LOCATION:https://researchseminars.org/talk/BeijingMoscowColloquium/15/
END:VEVENT
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