Calendar
- 26March 26, 2023No events
- 27March 27, 2023
CMSA Swampland Seminar: Recent developments on the tidal Love numbers of black holes
20 Garden Street, Cambridge, MA 02138Tidal Love numbers describe the deformability of compact objects under the presence of external tidal perturbations, and are found to be exactly zero for black holes in pure General Relativity. This property is however fragile, since they receive corrections from higher-order derivative terms in the theory. We show that the tidal deformability of neutral black holes is constrained by the Weak Gravity Conjecture. - 28March 28, 2023
Mathematical Picture Language Seminar: Non-positive sequences in analytic number theory & the Landau-Siegel zero
Abstract: A number of problems in analytic number theory can be reduced to showing that some related sequences are non-positive. In this direction a typical treatment is based on the idea of the Ʌ2 -sieve due to Selberg. We introduce a new approach that may find application to the Landau-Siegel zero problem.
The Math Picture Language seminar will be held via Zoom (not in person) at 9:30 a.m. Boston time.
Click the link for a Zoom Link for Tuesday Math Picture Language Seminars.
Recorded seminars can be viewed on the Mathemical Picture Language YouTube channel.Harvard–MIT Algebraic Geometry Seminar: The weight 0 compactly supported Euler characteristic of moduli spaces of marked hyperelliptic curves
1 Oxford Street, Cambridge, MA 02138 USAJoint work with Madeline Brandt and Siddarth Kannan. We use moduli spaces of G-admissible covers and tropical geometry to give a sum-over-graphs formula for the weight-0 compactly supported Euler characteristic of the moduli spaces H_{g,n} of n-marked hyperelliptic curves of genus g, as a virtual representation of S_n. Computer calculations then enable fully explicit formulas for the above in small genus. My aim is to make this talk accessible to anyone with passing familiarity with M_g and its Deligne-Mumford compactification.
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- 29March 29, 2023
Number Theory Seminar: Selmer averages in families of elliptic curves and applications
1 Oxford Street, Cambridge, MA 02138 USAOrbits of many coregular representations of algebraic groups are closely linked to moduli spaces of genus one curves with extra data. We may use these orbit parametrizations to compute the average size of Selmer groups of elliptic curves in certain families, e.g., with marked points, thus obtaining upper bounds for the average ranks of the elliptic curves in these families. (This is joint work with Manjul Bhargava.) We will also describe some other applications and related work (some joint with collaborators, including Levent Alpöge, Manjul Bhargava, Tom Fisher, Jennifer Park).
Joint MIT-Harvard-MSR Combinatorics Seminar: Hilbert series of matroid Chow rings and intersection cohomology
Starting with a matroid M one can construct three important algebraic objects: the Chow ring, the augmented Chow ring and the intersection cohomology module. They play instrumental roles within the proofs of the log-concavity of the Whitney numbers of the first kind, and the top-heaviness of the Whitney numbers of the second kind. We will describe the combinatorics of their Hilbert series for matroids in general and uniform matroids in particular. Several aspects such as unimodality, gamma-positivity and real-rootedness will be discussed under different perspectives. Based on joint work with Jacob Matherne, Matthew Stevens and Lorenzo Vecchi.
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For information about the Combinatorics Seminar, please visit…
http://math.mit.edu/seminars/c
ombin/ - 30March 30, 2023
CMSA General Relativity: Gravitational perturbations near to extreme Kerr
20 Garden Street, Cambridge, MA 02138Gravitational perturbations of a black hole illustrate the invaluable synergy between theory, experiment, and numerical simulations in general relativity. A recent development in the theory side has been the identification of the relevant degrees of freedom describing the low energy physics driving a black hole away from extremality. For simple cases, this low energy sector determines important aspects of the gravitational backreaction, and several properties that are key to our microscopic (quantum) understanding of black hole physics.In this talk I will discuss these developments in the context of the (near-)extreme Kerr black hole. In particular, I will revisit the spectrum of linear axisymmetric gravitational perturbations of this black hole. The aim is to characterise those perturbations that are responsible for the deviations away from extremality, and to contrast them with the linearized perturbations treated in the Newman-Penrose formalism. I will show that for Kerr the low-lying mode sector is subtle and intricate—features that their charged spherical symmetric cousins do not display. This unveils new clues on how to decode a microscopic, and holographic, understanding of the Kerr black hole.This seminar will be in person at CMSA, 20 Garden St, Room G-10, but will also be simultaneously broadcast over Zoom. For more information on how to join, please see: https://cmsa.fas.harvard.edu/event_category/general-relativity/
CMSA Active Matter: The Role of Orientational Order in Development
20 Garden Street, Cambridge, MA 02138Morphogenesis, the process through which genes generate form, establishes tissue scale order as a template for constructing the complex shapes of the body plan. The extensive growth required to build these ordered substrates is fueled by cell proliferation, which, naively, should disrupt order. Understanding how active morphogenetic mechanisms couple cellular and mechanical processes to generate order remains an outstanding question in animal development. I will review the statistical mechanics of orientational order and discuss the observation of a fourfold orientationally ordered phase (tetratic) in the model organism Parhyale hawaiensis. I will also discuss theoretical mechanisms for the formation of orientational order that require both motility and cell division, with support from self-propelled vertex models of tissue. The aim is to uncover a robust, active mechanism for generating global orientational order in a non-equilibrium system that then sets the stage for the development of shape and form.
This seminar will be held in person and on Zoom. For more information on how to join, please see: https://cmsa.fas.harvard.edu/event_category/active-matter-seminar/
Thursday Seminar: The coniveau tower
1 Oxford Street, Cambridge, MA 02138 USANo additional detail for this event.
Algebraic Dynamics Seminar: Arboreal Galois groups with colliding critical points
Let f(z) be a rational function of degree d>1 over a field K (usually K=C(t) or K=Q), and let x_0 be a point in P^1(K). The Galois groups of the equations f^n(z)=x_0 are known as arboreal Galois groups because they induce an action on a d-ary rooted tree. In 2013, Pink observed that when d=2 and the two critical points c_1, c_2 collide, meaning that f^m(c_1)=f^m(c_2) for some m>0, then the arboreal Galois groups are strictly smaller than the full automorphism group of the tree. We study these arboreal Galois groups when f is either a quadratic rational function or a cubic polynomial. When the critical points collide, we describe the maximum possible Galois groups in these cases, and we find sufficient conditions for these maximum groups to be attained.
For more information, please see: Algebraic Dynamics Seminar at Harvard
- 31March 31, 2023
CMSA Quantum Matter in Mathematics and Physics: A Plane Defect in the 3d O(N) Model
20 Garden Street, Cambridge, MA 02138It was recently found that the classical 3d O(N) model in the semi-infinite geometry can exhibit an “extraordinary-log” boundary universality class, where the spin-spin correlation function on the boundary falls off as (log x)^(-q). This universality class exists for a range 2≤N<Nc and Monte-Carlo simulations and conformal bootstrap indicate Nc>3. In this talk, I’ll extend this result to the 3d O(N) model in an infinite geometry with a plane defect. I’ll explain using the renormalization group (RG) that the extraordinary-log universality class is present for any finite N≥2, and that a line of defect fixed points is present at N=∞. This line of defect fixed points is lifted to the ordinary, special (no defect) and extraordinary-log universality classes by
1/N corrections. I’ll show that the line of defect fixed points and the 1/N corrections agree with an a-theorem by Jensen and O’Bannon for 3d CFTs with a boundary. Finally, I’ll conclude by noting some physical systems where the extraordinary-log universality class can be observed.
This seminar offers the option to attend by Zoom. For information on how to join, please see:Quantum Matter in Mathematics and Physics (QMMP) 2023:
https://cmsa.fas.harvard.edu/event_category/quantum-matter- seminar/ ——–
Subscribe to Harvard CMSA Quantum Matter and other seminar videos
(more to be uploaded):
https://www.youtube.com/playlist?list= PL0NRmB0fnLJQAnYwkpt9PN2PBKx4r vdup Subscribe to Harvard CMSA seminar mailing list:
https://forms.gle/1ewa7KeP6BxBuBeRA CMSA Quantum Matter in Mathematics and Physics: A Plane Defect in the 3d O(N) Model
20 Garden Street, Cambridge, MA 02138It was recently found that the classical 3d O(N) model in the semi-infinite geometry can exhibit an “extraordinary-log” boundary universality class, where the spin-spin correlation function on the boundary falls off as (log x)^(-q). This universality class exists for a range 2≤N<Nc and Monte-Carlo simulations and conformal bootstrap indicate Nc>3. In this talk, I’ll extend this result to the 3d O(N) model in an infinite geometry with a plane defect. I’ll explain using the renormalization group (RG) that the extraordinary-log universality class is present for any finite N≥2, and that a line of defect fixed points is present at N=∞. This line of defect fixed points is lifted to the ordinary, special (no defect) and extraordinary-log universality classes by
1/N corrections. I’ll show that the line of defect fixed points and the 1/N corrections agree with an a-theorem by Jensen and O’Bannon for 3d CFTs with a boundary. Finally, I’ll conclude by noting some physical systems where the extraordinary-log universality class can be observed.
This seminar offers the option to attend by Zoom. For information on how to join, please see:Quantum Matter in Mathematics and Physics (QMMP) 2023:
https://cmsa.fas.harvard.edu/event_category/quantum-matter- seminar/ ——–
Subscribe to Harvard CMSA Quantum Matter and other seminar videos
(more to be uploaded):
https://www.youtube.com/playlist?list= PL0NRmB0fnLJQAnYwkpt9PN2PBKx4r vdup Subscribe to Harvard CMSA seminar mailing list:
https://forms.gle/1ewa7KeP6BxBuBeRA Special Lecture on Complex Analysis/Probability Theory: "Jordan curves with piecewise geodesic property"
1 Oxford Street, Cambridge, MA 02138 USAThis talk will concern cyclic chains of arcs on the Riemann sphere such that each arc is a hyperbolic geodesic in the complement of the remaining arcs.
Location: Science Center 507 at 1:30pm on Friday, March 31st.
Please see the seminar page for more details: https://www.math.harvard.edu/~ctm/sem
- 01April 1, 2023No events