* Dates within the next 7 days are marked by a star.
Prof. Iván Blanco Chacón (U. Alcalá)
The LAC cryptosystem. A realistic alternative to Kyber?
* Today * Thursday 09 October 2025, 15:15, M3 (M234)
We discuss the LAC cryptosystem, which was presented to the NIST contest and although discarded in the outcome of the third round, was seriously considered as a rival for Kyber and is recently regaining attention from other different public committees.
One of the main features of LAC is the small modulus size, which is taken of the order of bytes, in comparison with Kyber, where q is at least 3329. This fact renders LAC one of the most compact cryptosystems, suitable to be used for small devices and with the same reduction security warranties as other RLWE-based schemes. However, the smallness of q brings an extra difficulty: the absence of NTT, which implies an obvious decrease in efficiency. This is overcome by the use of error correction in the cyphertext.
As proved by the authors, LAC outperforms Kyber at 128 and 256 bits security levels in terms of key size and cyphertext size while remaining more geneours in the security margin. It is true that these security levels are not recommended nowadays by NIST anymore, but the authors also suggested that LAC-192-v3b may be considered to achieve NIST Security Level 5 since it outperforms Kyber 1024 at this level. The goal of this talk is to report about this claim after the introduction of the foundations of the cryptosystem.
ANTA Seminar / Hollanti et al.
Dissertation
Okko Makkonen
PhD Defence: Algebraic methods for secure coded computing
* Friday 10 October 2025, 12:00, M1 (M232)
Further information
Thesis is available at: https://math.aalto.fi/en/current/#2188.
For Zoom streaming, click 'further info'.
ANTA Seminar / Hollanti et al.
Dr. Thomas Wasserman (Aalto University)
Continuous tensor categories and c=1 conformal field theories
* Tuesday 14 October 2025, 10:15, M3 (M234)
Some twenty years ago Fuchs, Runkel and Schweigert (FRS) established a perspective on so-called rational conformal field theories (cfts) that can be summarized by the slogan full cft = vertex operator algebra + topological quantum field theory. After describing this result, I will discuss work in progress joint with André Henriques and Adria Marin Salvador exploring it beyond rationality in the setting of full cfts at central charge c=1. One important aspect of rational cft is that it involves working with categories with only finitely many simple objects or categorical basis vectors. CFTs at c=1 behave in many ways like rational cfts, but in contrast with the rational case one needs to consider categories with infinitely many simple objects rather than just finitely many. As is familiar from undergraduate courses, working with infinitely many things is better with a topology around. I will discuss a setup (due to Marin) for talking about a category with a topological space of simple objects. After this I will explain how these continuous categories help understand the moduli space of c=1 conformal field theories and what this teaches us about pushing the FRS result beyond rationality.
Prof. Gretchen Matthews (Virginia Tech)
Success with Less: Data Recovery and Error Correction with Fewer Bits
* Tuesday 14 October 2025, 15:15, M1 (M232)
Further information
Linear codes are designed to protect data from loss and distortion. Data is stored with some redundancy that allows for the recovery of erasures or correction of errors. Decoding algorithms for linear codes typically take as input all symbols of a received word and attempt to determine the original codeword. In this talk, we focus on strategies that support error correction and erasure recovery using fewer bits than traditional approaches.
Prof. Gretchen Matthews (Virginia Tech)
(Colloquium talk) Success with Less: Data Recovery and Error Correction with Fewer Bits
* Tuesday 14 October 2025, 15:15, M1 (M232)
Further information
Linear codes are designed to protect data from loss and distortion. Data is stored with some redundancy that allows for the recovery of erasures or correction of errors. Decoding algorithms for linear codes typically take as input all symbols of a received word and attempt to determine the original codeword. In this talk, we focus on strategies that support error correction and erasure recovery using fewer bits than traditional approaches.
Charul Rajput
On function-correcting codes for locally bounded functions
* Wednesday 15 October 2025, 14:00, M2 (M233)
Function-correcting codes (FCCs), introduced by Lenz et al. (2023), generalize classical error correction by guaranteeing correct evaluation of a target function even when the transmitted data is corrupted. This talk begins with an overview of FCCs and the associated notation, then introduces locally (ρ,λ)-bounded functions, i.e., functions that take at most λ values within any Hamming ball of radius ρ. This local structure provides a natural setting for FCC design. An upper bound on redundancy is derived via the minimum length of an error-correcting code with given codebook size and distance, and a sufficient condition for optimality is established for the case λ=4. Further, it has been shown that any function can be represented in this framework, illustrated through Hamming-weight distribution functions. Lastly, the talk briefly discusses a generalized setting of FCCs that also considers data protection.
ANTA Seminar / Hollanti et al.
Prof. Christian Webb (University of Helsinki)
Fractional charge correlation functions in the sine-Gordon model and twisted fermions
Tuesday 21 October 2025, 10:15, M3 (M234)
The sine-Gordon model is a fascinating model of two-dimensional quantum field theory. It is not a conformal field theory, but it is believed to enjoy many interesting properties. This talk will focus on one of these properties known as bosonization. I will discuss how at the so-called free fermion point of the model, certain correlation functions of the sine-Gordon model are tau functions related to two-dimensional Dirac operators with twisting. This talk is based on joint work with Roland Bauerschmidt and Scott Mason.
Theo Elenius
TBA
Wednesday 22 October 2025, 10:15, M3 (M234)
Seminar on analysis and geometry
Hanz Cheng
Model order reduction via domain decomposition and the partition of unity condensed pole interpolation (PU-CPI)
Wednesday 22 October 2025, 14:00, M3 (M234)
In this talk, we discuss the PU-CPI, first developed in [1], which allows to construct a reduced order model which approximates the eigenvalues of an elliptic operator accurately and efficiently. The PU-CPI is a domain decomposition technique where local subdomain solutions are used to perform model order reduction via RayleighRitz projections. These local subspaces are constructed independently of each other, using data only related to the corresponding subdomain, resulting in a method that can be fully parallelized. Moreover, communication is only needed at the beginning and at the end, namely for distributing the local data, and for transferring the computed local results at the end of each task, respectively. Numerical examples will also be presented to illustrate the efficiency of the method.
[1] A. Hannukainen, J. Malinen, and A. Ojalammi. Distributed solution of laplacian eigenvalue problems. SIAM Journal on Numerical Analysis, 60(1):76103, 2022.
Numerical Analysis seminar
Dr. Augustin Lafay (Aalto University)
TBA
Tuesday 28 October 2025, 10:15, M3 (M234)
Henri Lahdelma
TBA
Wednesday 29 October 2025, 10:15, M3 (M234)
Seminar on analysis and geometry
Prof. Gerardo Barrera (Instituto Superior Técnico Lisboa)
Asymptotic Behavior of the Condition Number of Random Circulant Matrices
Wednesday 29 October 2025, 14:15, M2 (M233)
We analyze the asymptotic distribution of the extremal singular values of random circulant matrices generated by sequences of independent and identically distributed random variables satisfying the Lyapunov condition. Under an appropriate normalization, we establish that, as the matrix dimension tends to infinity, the joint distribution of the largest and smallest singular values converges in distribution to the independent product of Rayleigh and Gumbel laws. This result directly implies that a suitably normalized condition number of such matrices converges in distribution to a Fréchet law in the large-dimensional limit. The condition number serves as a quantitative measure of the sensitivity of linear systems to infinitesimal perturbations of the input. The proof relies on the classical coupling method of EinmahlKomlósMajorTusnády to achieve precise probabilistic control over the spectral extremes. This is a joint contribution with Paulo Manrique (Extremes, 2022).
Stochastics Seminar
Prof. Tuomas Hytönen (Aalto University)
TBA
Tuesday 09 December 2025, 15:15, M1 (M232)
TBA
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