Seminars

Predicting the dynamical behavior of complex systems poses a fundamental challenge in describing diverse phenomena, from dynamical self-assembly to the thermodynamics of protein folding. In this context, a key consideration is the limitation imposed on the timescales involved in the dynamics. For quantum dynamics, the Heisenberg’s uncertainty principle quantifies this limit, while for classical systems, particularly those exhibiting chaos, the Lyapunov time provides a characteristic timescale on which the system transitions to chaotic behavior. This raises a compelling question: are there bounds on timescales for deterministic systems evolving in phase space? In this talk, I will address this question by demonstrating that the time evolution of local Lyapunov exponents and entropy flow obey fundamental bounds which we can express as speed limits. The mathematical forms of our classical speed limits [1, 2] bear striking similarities to the well-known quantum speed limits. Our derivation employs a classical density matrix framework [3, 4] which offers an alternative computationally tractable basis for the statistical mechanics of non-equilibrium systems. These speed limits apply broadly to dynamical systems that are open or closed, conservative or dissipative, actively driven or passively evolving. References: [1] Swetamber Das and Jason R. Green, Speed limits on deterministic chaos and dissipation, Phys. Rev. Res. (Letter), 5:L012016 (2023). [2] Swetamber Das and Jason R. Green, Maximum speed of dissipation, Phys. Rev. E (Letter) 109(5) L052104 (2024). [3] Swetamber Das and Jason R. Green, Density matrix formulation of dynamical systems, Phys. Rev. E, 106:054135 (2022). [4] Swetamber Das and Jason R. Green, Spectral bounds on the entropy flow rate and Lyapunov exponents in differential dynamical systems, J. Phys. A: Math. Theor. 58(3) 035003 (2025).

Astrophysical jets associated with supermassive black holes (BHs) are believed to derive their power from the rotational energy of the BH itself, akin to how the Crab Nebula is powered by its pulsar. The Blandford-Znajek (BZ) mechanism, an electromagnetic Penrose process, provides a framework for understanding the physics of jet energetics. Specifically, it predicts the jet efficiency—the ratio of outflowing jet power to inflowing accretion power—to scale quadratically with the magnetic flux at and angular velocity of the black hole horizon. For rapidly spinning Kerr BHs, numerical simulations reveal jet efficiencies exceeding unity, a clear indicator of energy extraction from the black hole. At moderate spins, confirmation of energy extraction relies on the alignment of measured jet efficiencies with the BZ prediction. Over the past decade, this prediction has been validated across Kerr BHs with varying spin values. We present new findings from a large suite of magnetohydrodynamics accretion simulations conducted in spinning non-Kerr spacetimes, demonstrating that the BZ mechanism operates universally, extending its applicability to arbitrary BHs.

Topological combinatorics is a very young and exciting field of mathematical research at the crossroads of algebraic topology and discrete mathematics. Over the last forty years, it has gained popularity due to growing applications in math, computer science, and other applied areas. To be precise, this field is concerned with solutions to combinatorial problems related to fair division, graph coloring, evasiveness of graph properties etc., by applying sophisticated topological tools such as the Borsuk-Ulam theorem, characteristic classes, Morse theory and spectral sequences. In this talk, I will focus mainly on the topological spaces that arise in the context of various graph properties and their applications. I will start from the origins of this subject, i.e., Lovasz's striking proof of Kneser's conjecture from 1978. Then, I will describe the neighborhood complexes, independence and matching complexes, also mention some of the important applications. I plan to end with some recent work on newly discovered complexes.

Acute Promyelocytic Leukaemia (APL) arises from an aberrant chromosomal translocation involving the Retinoic Acid Receptor Alpha (RARA) gene, predominantly with the Promyelocytic Leukaemia (PML) or Promyelocytic Leukaemia Zinc Finger (PLZF) genes. The resulting oncoproteins block the haematopoietic differentiation program promoting aberrant proliferative promyelocytes. Retinoic Acid (RA) therapy is successful in most of the PML::RARA patients, while PLZF::RARA patients frequently become resistant and relapse. Recent studies pointed to various underlying molecular components, but their precise contributions remain to be deciphered. We developed a logical network model integrating signalling, transcriptional and epigenetic regulatory mechanisms, which captures key features of the APL cell responses to RA depending on the genetic background. The explicit inclusion of the histone methyltransferase EZH2 allowed the assessment of its role in the resistance mechanism, distinguishing between its canonical and non-canonical activities. The model dynamics was thoroughly analysed using tools integrated in the public software suite maintained by the CoLoMoTo consortium (https://colomoto.github.io/). The model serves as a solid basis to assess the roles of novel regulatory mechanisms, as well as to explore novel therapeutical approaches in silico.

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Pattanam, identified recently as the legendary port of Muziris, was a pivotal node in global trade networks spanning southern China to southern Spain, offering valuable insights into the socio-economic systems of the Sangam Age - an era characterized by pluralism, ecological balance and equitable trade practices devoid of standardized currency.

TBA

Advancements and upgradations of particle colliders and accelerators made it possible to study the heavy hadrons and tetraquarks. For example the LHCb Collaboration discovered the doubly charm tetraquark (T_cc) in the year 2022, and it also observed the B_s -> K semi leptonic decay in 2021. In this situation it has become important to study these processes on lattice. In our previous works we studied the spectrum of singly, doubly and triply heavy bottom hadron and doubly heavy tetraquark using NRQCD for bottom and HISQ for up/down, strange and charm quark. We also studied the form factors of B_s -> K semileptonic decay. We faced some issues while carrying out those studies and I will discuss how we addressed them.

We analyze the Large Hadron Collider potential to study triple couplings of the electroweak gauge bosons using their boosted hadronic decays. Deviations from Standard Model predictions spoil cancelations present in the standard model leading to the growth of the electroweak diboson production cross section at high center-of-mass energies. In this kinematical limit, the W and Z’s are highly boosted, and consequently, we study their hadronic decays into fat jets. Here, we show that the study of boosted hadronically decaying W and Z leads to limits on triple gauge couplings that are comparable to the ones originating from the leptonic decay channels.

The Left-Right Symmetric Model (LRSM) offers a compelling beyond the Standard Model (BSM) framework. Its potential derivation from grand unified symmetries like SO(10) or E6 further enhances its theoretical appeal. While conventional LRSM faces stringent constraints, particularly from the flavor sector, the Alternative Left-Right Model(ALRM) emerges as a less constrained scenario. ALRM introduces distinct particle content, including additional quarks and leptons. Among these, an exotic neutral lepton serves as a promising dark matter candidate, stabilized by an added global symmetry. Furthermore, the neutral component of one of the additional Higgs doublets in the model can also act as a scalar dark matter candidate within favorable kinematic regimes. This talk will provide a broad introduction to ALRM, discuss current experimental constraints, and explore the viability of its dark matter candidates.

TBA

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Regulation of gene expression is the key to sustaining organismal fitness in a changing environment and often involves interactions among many biochemical species. Identifying network motifs as functional building blocks of such interaction patterns has considerably reduced the complexity of analyzing gene regulation using coarse-grained mathematical models. By and large, the over-representation of genetic motifs has been studied based on their dynamics. In this talk, we will showcase how ingredients from information theory can be applied to understand the ubiquity of these regulatory motifs. Furthermore, we will demarcate the nontrivial connections between information processing and the inherent stochasticity or “noise” in gene regulation, emphasizing that the latter should not be viewed as a hindrance to the functioning of genetic motifs. Join Zoom Meeting https://zoom.us/j/2884416023 Meeting ID: 288 441 6023 Passcode: physbio

I will introduce an exactly solvable 2D lattice model with a large number of distinct topological phases with non-invertible symmetries. In all these topological phases (with topological ground state degeneracy), a commutative stabilizer monoid of Hermitian operators leave the ground state invariant and can also distinguish *all* local excitations, Furthermore, there are fractonic excitations which are confined and which change the nature of deconfined excitations. Remarkably, in all these phases, one can construct a spectral monoid, which is a non-trivial generalization of the creation and annihilation operators of quantum field theory, The spectral monoid is a monoid, includes the commutative stabilizer monoid and generates all the excitations acting on the ground state. This can be used to define the fusion rules for the excitations which are associative, but non-commutative non-Abelian and also non-unital. The dynamics is best described in terms of generalized free fields which can be used to construct deformations of each of the topological phases under which the ground state changes adiabatically. At the boundary of the phases, there exists novel quantum liquids where the fractonic excitations deconfine. These topological phases also have unusual entanglement properties. The entanglement entropy of a sub-region depends not only on the length of the boundary but also on its shape and the lattice, while the mutual information of subregions have different properties from other known gapped systems with anyonic excitations (e.g. stabilizer codes). Finally, I will discuss deformations of the above phases which create strongly correlated topological phases with unusual long-range correlations (unrelated to the topological nature) and enhanced anomalous entanglement properties. These stranger topological phases can harbor a fracton liquid. We will discuss if entanglement can be used to classify the topological phases in 2D lattices.