Department of Theorecal Physics

Faculty Members Type to enter text Mustansir Barma Welcome to the Department of Theorecal Physics at TIFR, Mumbai. Rajeev Bhalerao We are interested in the theorecal descripon of our universe over Kedar Damle a huge energy range, from fundamental Planck scale of 1028 eV in Basudeb Dasgupta - string theory to ultra-low energy scales of 10 13 eV in cold atomic gases Saumen Daa and everything in between. The research acvity in the department has Deepak Dhar four broad focus areas: condensed maer and stascal physics, Amol Dighe cosmology and astro-parcle physics, high energy physics, string theory Rajiv Gavai and mathemacal physics. Our research interests overlap across these Sourendu Gupta areas. Rishi Khatri

2014-02-19Subhabrata Majumdar 19:13:33 1/1 Unnamed Doc (#1) Gautam Mandal We try to find new laws of nature as well as novel manifestaons of Nilmani Mathur known laws. We try to find exact soluons, and develop approximaons Shiraz Minwalla as well as numerical techniques to understand the complex Sreerup Raychaudhuri phenomena occurring in the universe. For a peek into this fascinang Tuhin Roy world, keep reading ..... and visit our website at Rajdeep Sensarma Rishi Sharma www.theory.fr.res.in K. Sridhar Department of Theorecal Physics, Vikram Tripathi Tata Instute of Fundamental Research Sandip Trivedi Homi Bhabha Road, Colaba Mumbai 400005 More is different -- P. W. Anderson Condensed Maer and Stascal Physics

Welcome to the theorecal condensed We aempt to extend the use of maer and stascal physics group in stascal physics model to other the department. We have two broad disciplines to build models of stock focus areas: applicaon of classical stascal mechanics models to diverse markets, biological growth and physical phenomena , and explanaon protein folding etc. Non-equilibrium of the emergent properes of strongly models of aggregaon and chipping interacng quantum many-body have been studied to model systems. A Pattern produced molecular transport in cells. by Eulerian walkers

A system of many interacng parcles can exhibit qualitavely different behavior from a single or a few parcles. Interacons can lead to emergent phenomena like magnesm, superconducvity or superfluidity etc. where the behavior of the system changes suddenly as parameters like temperature or magnec field are varied. Condensed maer theory provides the tools to understand the stac and dynamic properes of these systems.

If the interacons between the parcles are stronger than their kinec energy,the theorecal descripon becomes immensely complicated. For high temperature superconductors, the well known pillars of solid state physics like band theory, Fermi liquid theory and BCS theory of superconducvity, all fail and we have to search for new

This simple picture of a compeon between kinec and interacon Some topics we work on: energies is complicated by the presence of frustraon, which leads to degeneracies in the system. We are interested in understanding • Realisc models of the glassy state with broken ergodicity. how these systems explore the phase space. • Equilibrium (solid-fluid) and non-equilibrium (jamming) phase transions in systems with hard core repulsion. • Proporonate growth in animals, protein- folding, global climate as non equilibrium steady state of periodically driven systems. • Agent based models of markets and opinion formaon.

Spin orbit coupling • Physics of high Tc superconductors. Magnec response of Mo insulators with in cold atoms • interesng magnec properes. Effect of spin and charge impuries on spin Materials in the laboratory inevitably have a lot of dirt and we study • liquids and topological insulators. the effects of spin and charge impuries on the properes of novel • Detailed phenomenology of diluted magnec states like quantum spin liquids and topological insulators and its semiconductors and granular superconductors connecon with the well known Kondo effect in metals. • Phenomenology of graphene and related materials. We also study the properes of ultracold atomic gases, where • Search for novel equilibrium and non- models relevant to other condensed maer system can be designed equilibrium states with ultracold atomic gases. with easily tunable parameters. In these systems, we also study • Development of techniques to understand non-equilibrium dynamics of strongly interacng quantum real me response of strongly interacng systems. many-body systems, a field which has opened up in recent years.

Members: Mustansir Barma Deepak Dhar Kedar Damle Rajdeep Sensarma Vikram Tripathi Cosmology and Astroparcle Physics

Cosmological research has entered its golden age. Long abounding in theories but lacking enough data, over the last quarter century it has entered the realm of ‘precision science’. The area has seen emergence of the so called ’Standard Cosmological Model’, where the structure, evoluon and nature of the universe and all its contents are beaufully described by few parameters which are now being determined with increasing precision. And yet, the more we unravel, the more mysteries we find - the mystery of dark maer and dark energy, the paradigm of inflaon, the violent explosions and energecs, the mind-boggling large structures and the onset and end of the dark ages in our universe. Even knowledge of our own Milky Way has to be embedded in our knowledge of the cosmos. Cosmology is an area of science that assimilates ideas from all branches of physics – for example, general theory of relavity, which tells us how the universe grows in size or how light is lensed by maer, quantum field theory in the early universe, nuclear physics describing how different elements came into being, plasma physics and fluid mechanics, which governs the interacon of photons and maer, to Newtonian gravity which determines local dynamics in galaxies and cluster of galaxies. The field is also unique in the connecon it makes between the very large and the very small – for example, one way to search for the invisible dark maer that constutes roughly one quarter of our universe is to do parcle physics experiments like those at the LHC. In fact, there are massive surveys some of which are taking place now and some are being planned to start in the future, like Planck, DES, EUCLID, LSST, SKA, etc with aim of understanding our universe. Cosmology and Astroparcle Physics is the newest sub-area of research in the department and is poised for rapid growth. Its present members include Subhabrata Majumdar and Rishi Khatri, who work on both theorecal and observaonal cosmology. Sandip Trivedi is interested in cosmology from perspecve of string theory. Amol Dighe and Basudeb Dasgupta are interested in astroparcle physics: the implicaons of the standard model of parcle physics for astronomical systems. The main research areas in CAP are movated by the vision which tries to address the following big quesons • What are dark maer and dark energy? • What causes cosmic inflaon ? • What goes on inside galaxies? • When did the universe end its dark ages and how? The(space(density(of(clusters(with(redshi7( • How has the universe evolved over me? • What are the signatures of early universe physics

Cosmology(with(clusters( that can be probed? • What role does neutrinos play in our universe? Some specific topics that are of current interest are: •The informaon hidden in the spectral distorons of the cosmic microwave background • Esmang the parameters of the standard model of cosmology by combining probes of cosmic microwave background (CMB), supernovae (SNe) , baryon acousc oscillaons (BAO) and galaxy clusters. •Involvement in surveys to probe dark maer and dark energy. The data from these surveys are also used to understand the growth of structures seeded by inial perturbaons on a smooth universe due to Inflaon. Thus connecons are made between the very early and late universe. The large scale structure that one finds from the survey data can also be used to look for deviaons from Einstein’s theory of gravity. •Topics at the interface of string theory and cosmology include cosmological string compacficaons and the role of AdS/CFT in understanding the resoluon of cosmological singularies. • Since visible maer trace the dark universe, considerable effort is given to study the synergies between cosmology and visible traces, their physics, energecs, structure and evoluon. These can be connected to studies of the distoron of the CMB at small scales. •Topics in astro-parcle physics including neutrino mass constraints from cosmological surveys and the role of neutrinos in the spectacular supernova explosion, baryogenesis and nucleosynthesis.

Members: Basudeb Dasgupta Members: Amol Dighe Subhabrata Majumdar Sandip TrivediAmol Dighe Rishi Khatri Subhabrata Majumdar Sandip Trivedi High Energy Physics

Parcle physics is the study of the basic structure of maer using the language of relavisc quantum field theories. These theories then predict exoc parcles and their properes, the outcomes of a variety of high-energy collider experiments such as at the LHC, the RHIC and the FAIR, as well as of high-energy cosmic phenomena such as in supernovae, neutron stars and the hot environment of the early universe. The building of models, as well as exploraon of their implicaons are pursued in the department.

The interacons of various kinds of maer are organized by the symmetry of the interacon. The standard model of parcle physics combines the strong with the electric and weak interacons. This uses the gauge symmetry SU(3)XSU(2)XU(1). All parts of this are subjects of intense invesgaon all over the world, and in our department.

Now that the Higgs parcle has been discovered in experiments at the LHC, those of us who are interested in the SU(2)XU(1) (also known as the electro-weak part because it combines electromagnesm with the weak interacons) part of the standard model are focussing on the idenficaon of physics which lies beyond the standard model. Are there new parcles? Are there new interacons? Are there new symmetries? An interesng theory for physics beyond the standard model is supersymmetry which posits a symmetry between fermions and bosons, and has been an important focus of research done here. Another possibility is that the universe has spaal dimensions other than the three we see in daily life.

One way to invesgate these possibilies is via colliding parcles at energies well above the Higgs mass. We hope that the upcoming results from higher energy collisions at the LHC will shed light on all these fundamental quesons. Another way to study the physics of the electro-weak interacons and physics beyond standard model is via neutrino oscillaons and the physics of quark flavor transformaons: research also pursued at the department.

2.4 The study of quarks and gluons, ie, the strong interacon, brings us to the 2.0 SU(3) part of the standard model. This is called Quantum Chromo 1.6 (GeV) c Dynamics (QCD). Strong interacons have generated the maximum η 1.2 number of Nobel prize winning ideas in physics, and is a very ferle field

m - 3/2 0.8 of research. Some of these quesons require us to do quantum field 0.4 theory on supercomputers. For example, we use supercomputers to

0.0 + + + + - - - - 1/2 3/2 5/2 7/2 1/2 3/2 5/2 7/2 study the composion, masses and interacons of exoc hadrons. Spectra of Triply Heavy Baryons

In parcle physics, as elsewhere, more can be different. The stascal mechanics of quarks gives rise to many different states of maer. We study the phase diagram of quarks and hadrons; a weird new phase is a plasma of quarks and gluons (QGP). This may be formed in the collisions of heavy nuclei at high-energy colliders, where it can be studied using the fluid dynamics of relavisc maer. The QGP is also important for an understanding of the early universe. Neutron stars, on the other hand, could have superconducng phases of QCD, which could affect their visible properes.

Members: Rajeev Bhalerao Saumen Daa Amol Dighe Rajiv Gavai Sourendu Gupta Nilmani Mathur Sreerup Raychaudhuri Tuhin Roy Rishi Sharma K Sridhar String Theory and Mathemacal Physics

The standard model of parcle physics - which accounts for all observed fundamental forces except gravity - is formulated within the framework of quantum field theory. The `standard model' of cosmology, in which gravitaonal physics plays a fundamental role, is formulated largely within the theory of classical (or semiclassical) fields interacng with a dynamical but classical space-me geometry. Any aempt to describe phenomena for which quantum fluctuaons of space-me are important appears to require a framework that generalizes and subsumes these two frameworks. String theory is an aempt to construct such a framework. There are two broad themes of research in string theory. The first is to try to understand the space of vacua of string theory in order to idenfy the string vacuum that might describe the observed universe. The second is to study specially simple and symmetric string vacua in detail, in order to derive universal general lessons about quantum gravitaonal dynamics. A key tool in this second endeavor is the AdS/CFT correspondence, a remarkable conjecture that provides a nonperturbave descripon of the gravitaonal dynamics about some of the vacua of string theory in terms of a (conceptually) well understood non gravitaonal quantum field theory. Somewhat surprisingly, the detailed study of specially simple string vacua has substanally broadened our understanding of the dynamics of strongly coupled quantum field theories in general, and is increasingly proving useful in the study of strongly coupled dynamics in diverse areas of physics - from QCD to some systems in condensed maer physics. This study has also made contribuons to ongoing research in modern mathemacs. Members of the string group in TIFR contribute to both these broad streams of research, but especially to the second stream. confinement/deconfinement phase deconfinement phase transition in 4dYM.

confinement phase IIA SUGRA 4dYM W 0=0

W 4≠0

W 4≠0 AdS D4 soliton W ≠0 W 0 4 0= AdS -SYM Phase diagram W 0≠0 SS transition

W ≠0 0 Black D4 W 4=0

Some quesons that the group has recently focussed on are listed below: • Construcon and classificaon of string vacua, dynamics and stability of compacficaons. • Microscopic and macroscopic descripons of black hole entropy, the entropy funcon formalism, computaon of topological indices, subleading quantum and higher-derivave correcons, marginal decays of black holes. • The relaonship between gravity and fluid dynamics, generalizaons of hydrodynamical equaons, transport properes of strongly interacng maer at high densies and temperatures, superconductors and superfluids. • Nonperturbave properes of string theory using M-theory, dynamics and symmetries of mulple membranes and five-branes. • New examples and limits in AdS/CFT, non-supersymmetric AdS compacficaons in string theory, new black hole soluons and their dual field theory descripons, black hole - black string phase transions. • Confinement, chiral symmetry breaking and the dynamics of gauge theories, non- relavisc limits of field theory, Lifshitz scaling, RG flows, phase diagram of gauge theories in low dimensions at large N. • New formulaons for string dynamics, matrix theory, low-dimensional string vacua. • The study of nonsupersymmetric strong weak coupling dualies in quantum field theories in three dimensions, and the relaonship to anyonic stascs.

Members: Members: Gautam Mandal Shiraz Minwalla Sandip Trivedi Amol Dighe Subhabrata Majumdar Sandip Trivedi