Bibhushan Shakya's webpage

Research 

I am interested in understanding the fundamental structure of nature - what its basic constituents are, and how they came to be at the beginning of the Universe. For details of my publications, see my pages on INSPIRE or the arXiv. 

The Early Universe in Gravitational Waves

The first one second of the Universe was the most important: this is the period when the Universe underwent rapid superluminal expansion (inflation), when a grand unified structure evolved into the forces and particles we know of today, and all of matter was created, including the generation of dark matter and an asymmetry between matter and antimatter. Very little is known about this period from experimental observations. I am interesting in piecing together what happened in this early phase of the Universe. In this direction, I am particularly interested in the possibility to learn about this early epoch through current and upcoming gravitational wave experiments, which provide an unprecedented opportunity to directly observe signals from energetic events in the early Universe. 

   Cosmic Colliders: The early Universe could have gone through phase transitions, where a stable phase emerged via the nucleation of bubbles of true vacuum, which expanded with ultrarelativistic speeds and collider with each other. Such ultrarelativistic collisions can act as epic cosmic scale high energy colliders, the most violent events in the history of our Universe that can provide access to high energy physics far beyond any energy scale or temperature ever reached. I am currently leading the research program to understand the physics and applications of such “cosmic colliders”.

   The Tachyonic Higgs: One of the most remarkable implications of the current measurements of the properties of the fundamental particles is that the Higgs boson develops an instability at large values. In this unstable regime, the Higgs becomes tachyonic: its mass becomes imaginary. While the present Universe does not know about this tachyonic region, it is possible that this tachyonic regime could have been briefly realized in the earliest moments of the Universe, triggering a violent instability in parts of the early Universe. One of my primary research directions is to figure out how we could tell if this happened, and what significance it could have for the existence of the Universe as we know it today.

Dark Matter Phenomenology

Dark matter is the most abundant form of matter in the Universe, about five times more abundant than all the other particles known to us. The identity of dark matter remains one of the leading questions in particle physics, and observing its non-gravitational interactions has been one of the major programs in particle physics research over the past few decades. I think about various theoretical models of dark matter, how to probe them experimentally, and whether any of the recent anomalous results from various experiments could mean that we have finally observed dark matter interactions. 

Extended Neutrino Sectors and their Phenomenology

The neutrino sector of the Standard Model likely features extensions to new physics. I am interested in investigating possible connections between the neutrino sector and other aspects of particle physics (such as dark matter, supersymmetry, hidden sectors, and exotic signals at low energy experiments).

New physics searches at Large Hadron Collider (LHC):

The Large Hadron Collider is exploring energy scales that we have never directly explored before, and the data it is gathering offers us unprecedented opportunities to explore physics beyond the Standard Model at the TeV scale. My research looks at possibilities for discovering signatures of well-motivated particle physics extensions, such as supersymmetry, or extended neutrino/dark sectors, in the upcoming runs.

Other Activities 

In the past few years, I have been heavily involved in the BCVSPIN program (https://www.bcvspin.org/), the particle physics and cosmology program for South Asian countries.