The Department of Theoretical Physics

In everyday life, a gentle nudge at the right moment can prevent a system from spiraling - resetting a frozen computer, rebooting a router, or tapping a malfunctioning machine. The researchers show that a similar idea works in physics, but with a deeper consequence. "The most surprising insight is that you can reshape the entire phase behavior of a many-body system without ever touching the interactions or the majority of its degrees of freedom," says Prof. Shamik Gupta. "In statistical physics, the orthodoxy is that to change a phase transition, you must change couplings, external fields, geometry, or temperature. Yet this study shows that you can move, split, eliminate, or recreate phase transitions exactly as you like, simply by occasionally resetting a small fraction of the system to a chosen state."

At the heart of the mechanism is non-equilibrium dynamics. "Resetting breaks detailed balance, thereby inducing a nonequilibrium structure. It biases macroscopic order indirectly through the reset subsystem, exploits long-range interactions to propagate that bias, and turns memory effects into a stabilizing force," Gupta adds. "Control emerges from an intricate interplay of noise, memory, and incomplete intervention."

This work by Anish Acharya, Rupak Majumder, and Prof. Shamik Gupta has been published in Physical Review Letters.

The IMPETUS initiative is a phased national program aimed at establishing an end-to-end Indian precision experiment based on the positronium system. The initiative aligns with listed goals both in the DAE Vision-2047 the Mega Science Vision (MSV) documents in nuclear and particle physics. It seeks to build a coordinated and interdisciplinary national effort that integrates expertise across high-energy physics, nuclear physics, optics, materials science, detector development, and data science to perform world-leading precision studies of positronium decays and rare processes.

The program will enable best-in-class searches for physics beyond the Standard Model (BSM), including milli-charged particles, axion-like particles, Z′ resonances, and electromagnetic moments of the dark matter, while also advancing fundamental tests of discrete symmetries and quantum correlations. In parallel, this initiative will leverage the same detector platform for interdisciplinary applications such as quantum entanglement studies, precision nuclear form-factor measurements, quantum sensing, and the development of advanced medical imaging technologies.

DTP members finds a new way to derive the effective infrared of a strongly coupled QCD.

New class of CMB spectral distortions were predicted that arise from absorption of the CMB photons by multi-state dark matter. Such signatures are a natural prediction of a class of composite dark matter models characterized by electrically neutral states but with nonzero higher order electromagnetic moments. The nature of spectral distortions depends sensitively on the dark matter transition frequency and the strength of couplings of dark matter with visible sector particles as well as its self-interactions, thus opening a new window to probe the nature of dark matter. The non-thermal distortions thus created were computed and shown to have unique spectral shapes making them distinguishable from the standard thermal distortions and potentially detectable in the next-generation experiments such as Primordial Inflation Explorer (PIXIE). The spectral distortion limits from the cosmic background explorer/far-infrared absolute spectrophotometer (COBE/FIRAS) were computed and were found to already give a constraint on the electromagnetic coupling of dark matter, which is 3 orders of magnitude stronger compared to the current direct detection limits for the mass dark matter of the order of few times the electron mass and transition energy in the optical range.