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Volume 74, Nº 3 (2019)
- Ano: 2019
- Artigos: 10
- URL: https://journals.rcsi.science/0042-1316/issue/view/7510
Examples of solution of the inverse scattering problem and the equations of the Novikov–Veselov hierarchy from the scattering data of point potentials
Resumo
The inverse scattering problem is considered for the two-dimensional Schrödinger equation at fixed positive energy. The results include inverse scattering reconstructions from the simplest scattering amplitudes. In particular, a complete analytic solution is given of the phased and phaseless inverse scattering problems for single-point potentials of Bethe–Peierls–Fermi–Zeldovich–Berezin–Faddeev type. Numerical inverse scattering reconstructions from the simplest scattering amplitudes are then studied using the method of the Riemann–Hilbert–Manakov problem in soliton theory. Finally, these numerical inverse scattering results are used to construct corresponding numerical solutions of the non-linear equations of the Novikov–Veselov hierarchy at fixed positive energy.Bibliography: 21 titles.
Uspekhi Matematicheskikh Nauk. 2019;74(3):3-16
3-16
Conway topograph, $\mathrm{PGL}_2(\pmb{\mathbb Z})$-dynamics and two-valued groups
Resumo
Conway's topographic approach to binary quadratic forms and Markov triples is reviewed from the point of view of the theory of two-valued groups. This leads naturally to a new class of commutative two-valued groups, which we call involutive. It is shown that the two-valued group of Conway's lax vectors plays a special role in this class. The group $\mathrm{PGL}_2(\mathbb Z)$ describing the symmetries of the Conway topograph acts by automorphisms of this two-valued group. Binary quadratic forms are interpreted as primitive elements of the Hopf 2-algebra of functions on the Conway group. This fact is used to construct an explicit embedding of the Conway two-valued group into $\mathbb R$ and thus to introduce a total group ordering on it. The two-valued algebraic involutive groups with symmetric multiplication law are classified, and it is shown that they are all obtained by the coset construction from the addition law on elliptic curves. In particular, this explains the special role of Mordell's modification of the Markov equation and reveals its connection with two-valued groups in $K$-theory. The survey concludes with a discussion of the role of two-valued groups and the group $\mathrm{PGL}_2(\mathbb Z)$ in the context of integrability in multivalued dynamics.Bibliography: 104 titles.
Uspekhi Matematicheskikh Nauk. 2019;74(3):17-62
17-62
On the homotopy finiteness of DG categories
Resumo
This paper gives a short overview of results related to homotopy finiteness of DG categories. A general plan is explained for proving homotopy finiteness of derived categories of coherent sheaves and coherent matrix factorizations on separated schemes of finite type over a field of characteristic zero.Bibliography: 39 titles.
Uspekhi Matematicheskikh Nauk. 2019;74(3):63-94
63-94
$SU$-bordism: structure results and geometric representatives
Resumo
The first part of this survey gives a modernised exposition of the structure of the special unitary bordism ring, by combining the classical geometric methods of Conner–Floyd, Wall, and Stong with the Adams–Novikov spectral sequence and formal group law techniques that emerged after the fundamental 1967 paper of Novikov. In the second part toric topology is used to describe geometric representatives in $SU$-bordism classes, including toric, quasi-toric, and Calabi–Yau manifolds.Bibliography: 56 titles.
Uspekhi Matematicheskikh Nauk. 2019;74(3):95-166
95-166
167-184
Rational differential forms on the variety of flexes of plane cubics
Uspekhi Matematicheskikh Nauk. 2019;74(3):185-186
185-186
Maximum of a catalytic branching random walk
Uspekhi Matematicheskikh Nauk. 2019;74(3):187-188
187-188
Weak solvability and convergence of solutions for the fractional Voigt-$\alpha$ model of a viscoelastic medium
Uspekhi Matematicheskikh Nauk. 2019;74(3):189-190
189-190
Maximum defect of an admissible octahedron in a rational lattice
Uspekhi Matematicheskikh Nauk. 2019;74(3):191-192
191-192
Grigori Iosifovich Olshanski (on his 70th birthday)
Uspekhi Matematicheskikh Nauk. 2019;74(3):193-213
193-213