18 MAY 2025
11:00 - 12:30

Abstract:
I will talk about a work in progress about dispersion relations and tidal deformability of compact objects. Tidal Love number coefficient is given in terms of the two point function of the stress tensor. These are similar to the electromagnetic polarizability of an object. By using the conditions of causality and positivity one can prove positivity bounds on the Love number of weakly gravitating compact objects.

15 MAY 2025
14:00 - 16:00

An imaginary sort of a first-order structure is a possible universe of an interpretable structure. The significance of imaginary sorts was established in the abstract setting of Classification Theory by Shelah, where all notions of stability theory, especially algebraic closure, were interpreted with imaginary sorts taken into account. Imaginaries were studied for specific theories by Poizat who showed that algebraically closed fields and differentially closed fields eliminate imaginaries, i.e. each imaginary sort is in definable bijection with a definable set of n-tuples. In valued fields imaginary sorts differ qualitatively from definable sets; an example is the value group. In this case it is a question of finding a useful basis for the imaginary sorts, meaning that every imaginary sort can be embedded into a product of basis elements. A basis for imaginary sorts for algebraically closed valued fields was given by Haskell-Hrushovski-Macpherson. Rideau-Hrushovski-Martin, and more recently Hils-Rideau-Kikuchi, proved that for the field of $p$-adic numbers the $p$-adic lattices provide a basis for imaginary sorts.
In this talk I will describe joint work with Ehud Hrushovski which gives a description of imaginary sorts and their basis for products and restricted products of structures in terms of a basis for imaginary sorts for the factors. In 1959 Feferman and Vaught proved that the theory of a product is determined by the theory of the factors and the theory of the Boolean algebra of subsets of the index set. This yields decidability results and descriptions of definable sets for products in terms of the factors. Our results show that imaginaries also admit a description relative to the factors. The proofs use tools from geometric stability theory including liaison groups, and descriptive set theory of smooth Borel equivalence relations, including a dichotomy theorem due to Harrington-Kechris-Louveau and Glimm-Efros. As an application, we describe a basis for the imaginary sorts for the ring of adeles of rational numbers in terms of the family of $p$-adic lattices for �almost all� $p$, and prove weak elimination of imaginaries for the adeles in these sorts.

Joint work with: Ehud Hrushovski
Zoom room information:
https://us06web.zoom.us/j/81916335336?pwd=5zQT4lutMiBoY5Xp1pkFGtbqiaGozg.1
Meeting ID: 819 1633 5336
Passcode: 559618
Venue: Niavaran, Lecture Hall 1

14 MAY 2025
14:00 - 15:00

Retinal degenerative diseases including neovascular age-related macular degeneration (nAMD), diabetic retinopathy (DR), glaucoma, and retinitis pigmentosa (RP) are major global causes of vision loss. Current therapies, such as anti-VEGF treatments, face limitations due to biological complexity, treatment resistance, and delivery challenges. Our research integrates systems biology, molecular engineering, and gene therapy to address these gaps. We identify key molecular hubs and pathways, develop next-generation anti-angiogenic agents (hinge-truncated sFLT01), and design novel peptide-based gene delivery system (MiRGD) that enhances targeting and biocompatibility. Additionally, we explore optogenetic tools, ER stress modulation, and retinal regeneration strategies to advance therapeutic options. Our multidisciplinary approach offers promising avenues for safer, more effective treatments and deepens the understanding of retinal disease mechanisms.


This Seminar is free, hybrid, and open to the public.

14 MAY 2025
11:00 - 12:00

Abstract:

This talk addresses key challenges in modern cosmology and introduces the motivations for a "void-based cosmology". In this approach, voids (bubbles) are treated as independent, dynamic components of the cosmic web next to clusters (drops). Drawing inspiration from the behavior of heated milk overflowing, the presentation will examine the connection between void surface tension and the cosmological constant, the modified uncertainty principle, and the evolving dark energy density resulting from void mergers on cosmic scales.

Indico Link:
https://indico.hep.ipm.ir/e/e.yusofi

Link to Join Virtually:
https://www.skyroom.online/ch/ipm-particles/weekly-seminar

14 MAY 2025
14:00 - 15:00

For any k + 1 ≥ 3 positive integers t, n_1, . . . , n_k, there exists a positive integer N such that if every t-element subset of the set {1, . . . , N} is colored using one of the k colors 1, . . . , k, then there exists an index i ∈ {1, . . . , k} and a subset S ⊆ {1, . . . , N} with |S| = n_i, such that every t-element subset of S is colored with color i. This is a generalization of Ramseys Theorem, which is often formulated in the language of graph theory by:
? interpreting {1, 2, . . . , N} as the vertex set of the complete graph K_N,
? considering the case t = 2, and
? coloring each 2-element subset (edge) with one of k colors.
Ramseys Theorem then implies that for any two positive integers s and t, there exists a minimum integer N such that in any red-blue coloring of the edges of K_N , one can find either a red complete subgraph Ks or a blue complete subgraph Kt. The smallest such N is known as the Ramsey number R(s, t), or more generally R(G, H) when considering arbitrary graphs G and H. Several variants of Ramsey numbers have been developed. Notably, the bipartite Ramsey number, the multipartite Ramsey number, the m-bipartite Ramsey number, and the pair bipartite Ramsey number extend the classical notions to bipartite and multipartite settings.
In this talk, we will present recent results concerning some of these extended versions. In particular, we will focus on:
? The multicolor bipartite Ramsey number BR(G_1, G_2, . . . , G_t), defined as the smallest integer n such that any t-edge-coloring of the complete bipartite graph K_{n,n} contains a monochromatic copy of G_i for some 1 ≤ i ≤ t.
? The pair bipartite Ramsey number Bp(G_1, G_2) = (a, b), the smallest ordered pair such that every red-blue edge-coloring of K_{c,d} with c ≥ d guarantees a blue copy of G_1 or a red copy of G_2, provided c ≥ a and d ≥ b.

Zoom room information:
https://us06web.zoom.us/j/84906984159?pwd=BCWaIbXBuku3A5I84zNg9mHFxVZjXD.1
Meeting ID: 849 0698 4159
Passcode: 362880
Venue: Niavaran, Lecture Hall 1

14 MAY 2025
17:30 - 19:00

I will start with a review of KSB/A stability, especially their local version and then discuss joint work with Janos Kollar, showing that it is enough to check these conditions, including flatness, up to codimension 2. This implies that we have a very good understanding of this stability condition in general, because local KSB-stability is trivial at codimension 1 points, and quite well understood at codimension 2 points, since we have a complete classification of 2-dimensional slc singularities.

Venue: online
https://zoom.us/join
Meeting ID: 9086116889
Passcode: 362880
Website: http://math.ipm.ac.ir/agnt/
Venue: , (Online)