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Welcome to the Department of Theore1cal Physics at TIFR, Mumbai.
We are interested in the theore1cal descrip1on of our universe over
a huge energy range, from fundamental Planck scale of 1028 eV in
string theory to ultra-‐low energy scales of 10-‐13 eV in cold atomic gases and everything in between. The research ac1vity in the department has
four broad focus areas: condensed maKer and sta1s1cal physics,
cosmology and astro-‐par1cle physics, high energy physics, string theory
and mathema1cal physics. Our research interests overlap across these
areas.
We try to find new laws of nature as well as novel manifesta1ons of
known laws. We try to find exact solu1ons, and develop approxima1ons
as well as numerical techniques to understand the complex
phenomena occurring in the universe. For a peek into this fascina1ng
world, keep reading ..... and visit our website at
www.theory.1fr.res.in
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Department of Theore1cal Physics
Faculty Members Mustansir Barma Rajeev Bhalerao
Kedar Damle
Basudeb Dasgupta
Saumen DaKa
Deepak Dhar
Amol Dighe
Rajiv Gavai
Sourendu Gupta
Rishi Khatri
Subhabrata Majumdar
Gautam Mandal
Nilmani Mathur
Shiraz Minwalla
Sreerup Raychaudhuri
Tuhin Roy
Rajdeep Sensarma
Rishi Sharma
K. Sridhar
Vikram Tripathi
Sandip Trivedi
Department of Theore1cal Physics, Tata Ins1tute of Fundamental Research Homi Bhabha Road, Colaba Mumbai 400005
Condensed MaKer and Sta1s1cal Physics
Members: Mustansir Barma Deepak Dhar Kedar Damle Rajdeep Sensarma Vikram Tripathi
Welcome to the theore1cal condensed maKer and sta1s1cal physics group in the department. We have two broad focus areas: applica1on of classical sta1s1cal mechanics models to diverse physical phenomena , and explana1on of the emergent proper1es of strongly interac1ng quantum many-‐body systems. A system of many interac1ng par1cles can exhibit qualita1vely different behavior from a single or a few par1cles. Interac1ons can lead to emergent phenomena like magne1sm, superconduc1vity or superfluidity etc. where the behavior of the system changes suddenly as parameters like temperature or magne1c field are varied. Condensed maKer theory provides the tools to understand the sta1c and dynamic proper1es of these systems.
If the interac1ons between the par1cles are stronger than their kine1c energy,the theore1cal descrip1on 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 superconduc1vity, all fail and we have to search for new
We also study the proper1es of ultracold atomic gases, where models relevant to other condensed maKer system can be designed with easily tunable parameters. In these systems, we also study non-‐equilibrium dynamics of strongly interac1ng quantum many-‐body systems, a field which has opened up in recent years.
This simple picture of a compe11on between kine1c and interac1on energies is complicated by the presence of frustra1on, which leads to degeneracies in the system. We are interested in understanding how these systems explore the phase space.
Some topics we work on:
• Realis1c models of the glassy state with broken ergodicity. • Equilibrium (solid-‐fluid) and non-‐equilibrium (jamming) phase transi1ons in systems with hard core repulsion.
• Propor1onate growth in animals, protein-‐ folding, global climate as non equilibrium steady state of periodically driven systems. • Agent based models of markets and opinion forma1on.
• Physics of high Tc superconductors. • Magne1c response of MoK insulators with interes1ng magne1c proper1es. • Effect of spin and charge impuri1es on spin liquids and topological insulators. • Detailed phenomenology of diluted magne1c semiconductors and granular superconductors • Phenomenology of graphene and related materials. • Search for novel equilibrium and non-‐ equilibrium states with ultracold atomic gases. • Development of techniques to understand real 1me response of strongly interac1ng systems.
Materials in the laboratory inevitably have a lot of dirt and we study the effects of spin and charge impuri1es on the proper1es of novel states like quantum spin liquids and topological insulators and its connec1on with the well known Kondo effect in metals.
More is different -‐-‐ P. W. Anderson
We aKempt to extend the use of sta1s1cal physics model to other disciplines to build models of stock markets, biological growth and protein folding etc. Non-‐equilibrium models of aggrega1on and chipping have been studied to model molecular transport in cells.
Spin orbit coupling
in cold atoms
A Pattern produced by Eulerian walkers
Cosmology and Astropar1cle Physics
Members: Amol Dighe Subhabrata Majumdar Sandip Trivedi
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, evolu1on and nature of the universe and all its contents are beau1fully 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 maKer and dark energy, the paradigm of infla1on, the violent explosions and energe1cs, 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 and Astropar1cle 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 theore1cal and observa1onal cosmology. Sandip Trivedi is interested in cosmology from perspec1ve of string theory. Amol Dighe and Basudeb Dasgupta are interested in astropar1cle physics: the implica1ons of the standard model of par1cle physics for astronomical systems. The main research areas in CAP are mo1vated by the vision which tries to address the following big ques1ons
Cosmology and Astropar1cle Physics
Members: Basudeb Dasgupta Amol Dighe Rishi Khatri Subhabrata Majumdar Sandip Trivedi
Cosmology is an area of science that assimilates ideas from all branches of physics – for example, general theory of rela1vity, which tells us how the universe grows in size or how light is lensed by maKer, quantum field theory in the early universe, nuclear physics describing how different elements came into being, plasma physics and fluid mechanics, which governs the interac1on of photons and maKer, to Newtonian gravity which determines local dynamics in galaxies and cluster of galaxies. The field is also unique in the connec1on it makes between the very large and the very small – for example, one way to search for the invisible dark maKer that cons1tutes roughly one quarter of our universe is to do par1cle 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.
• What are dark maKer and dark energy?
• What causes cosmic infla1on ?
• What goes on inside galaxies?
• When did the universe end its dark ages and how?
• How has the universe evolved over 1me?
• What are the signatures of early universe physics that can be probed?
• What role does neutrinos play in our universe?
Some specific topics that are of current interest are:
•The informa1on hidden in the spectral distor1ons of the cosmic microwave background
• Es1ma1ng the parameters of the standard model of cosmology by combining probes of cosmic microwave background (CMB), supernovae (SNe) , baryon acous1c oscilla1ons (BAO) and galaxy clusters. •Involvement in surveys to probe dark maKer and dark energy. The data from these surveys are also used to understand the growth of structures seeded by ini1al perturba1ons on a smooth universe due to Infla1on. Thus connec1ons 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 devia1ons from Einstein’s theory of gravity. •Topics at the interface of string theory and cosmology include cosmological string compac1fica1ons and the role of AdS/CFT in understanding the resolu1on of cosmological singulari1es. • Since visible maKer trace the dark universe, considerable effort is given to study the synergies between cosmology and visible traces, their physics, energe1cs, structure and evolu1on. These can be connected to studies of the distor1on of the CMB at small scales. •Topics in astro-‐par1cle physics including neutrino mass constraints from cosmological surveys and the role of neutrinos in the spectacular supernova explosion, baryogenesis and nucleosynthesis.
Cosmology(with(clusters(
The(space(density(of(clusters(with(redshi7(
High Energy Physics Par1cle physics is the study of the basic structure of maKer using the language of rela1vis1c quantum field theories. These theories then predict exo1c par1cles and their proper1es, 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 explora1on of their implica1ons are pursued in the department.
The interac1ons of various kinds of maKer are organized by the symmetry of the interac1on. The standard model of par1cle physics combines the strong with the electric and weak interac1ons. This uses the gauge symmetry
SU(3)XSU(2)XU(1). All parts of this are subjects of intense inves1ga1on all over the world, and in our department.
Members: Rajeev Bhalerao Saumen DaKa Amol Dighe Rajiv Gavai Sourendu Gupta Nilmani Mathur
Sreerup Raychaudhuri Tuhin Roy Rishi Sharma K Sridhar
Now that the Higgs par1cle 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 electromagne1sm with the weak interac1ons) part of the standard model are focussing on the iden1fica1on of physics which lies beyond the standard model. Are there new par1cles? Are there new interac1ons? Are there new symmetries? An interes1ng 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 spa1al dimensions other than the three we see in daily life.
One way to inves1gate these possibili1es is via colliding par1cles 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 ques1ons. Another way to study the physics of the electro-‐weak interac1ons and physics beyond standard model is via neutrino oscilla1ons and the physics of quark flavor transforma1ons: research also pursued at the department.
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The study of quarks and gluons, ie, the strong interac1on, brings us to the SU(3) part of the standard model. This is called Quantum Chromo
Dynamics (QCD). Strong interac1ons have generated the maximum number of Nobel prize winning ideas in physics, and is a very fer1le field of research. Some of these ques1ons require us to do quantum field theory on supercomputers. For example, we use supercomputers to study the composi1on, masses and interac1ons of exo1c hadrons.
In par1cle physics, as elsewhere, more can be different. The sta1s1cal mechanics of quarks gives rise to many
different states of maKer. 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 rela1vis1c maKer. The QGP is also important for an understanding of the early
universe. Neutron stars, on the other hand, could have superconduc1ng phases of QCD, which could affect
their visible proper1es.
Spectra of Triply Heavy Baryons
String Theory and Mathema1cal Physics
Members: Amol Dighe Subhabrata Majumdar Sandip Trivedi
The standard model of par1cle 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 gravita1onal physics plays a fundamental role, is formulated largely within the theory of classical (or semiclassical) fields interac1ng with a dynamical but classical space-‐1me geometry. Any aKempt to describe phenomena for which quantum fluctua1ons of space-‐1me are important appears to require a framework that generalizes and subsumes these two frameworks. String theory is an aKempt 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 iden1fy 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 gravita1onal dynamics. A key tool in this second endeavor is the AdS/CFT correspondence, a remarkable conjecture that provides a nonperturba1ve descrip1on of the gravita1onal dynamics about some of the vacua of string theory in terms of a (conceptually) well understood non gravita1onal quantum field theory. Somewhat
surprisingly, the detailed study of specially simple string vacua has substan1ally 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 maKer physics. This study has also made contribu1ons to ongoing research in modern mathema1cs. Members of the string group in TIFR contribute to both these broad streams of research, but especially to the second stream.
Some ques1ons that the group has recently focussed on are listed below:
• Construc1on and classifica1on of string vacua, dynamics and stability of compac1fica1ons.
• Microscopic and macroscopic descrip1ons of black hole entropy, the entropy func1on formalism, computa1on of topological indices, subleading quantum and higher-‐deriva1ve correc1ons, marginal decays of black holes.
• The rela1onship between gravity and fluid dynamics, generaliza1ons of hydrodynamical equa1ons, transport proper1es of strongly interac1ng maKer at high densi1es and temperatures, superconductors and superfluids.
• Nonperturba1ve proper1es of string theory using M-‐theory, dynamics and symmetries of mul1ple membranes
and five-‐branes.
• New examples and limits in AdS/CFT, non-‐supersymmetric AdS compac1fica1ons in string theory, new black hole
solu1ons and their dual field theory descrip1ons, black hole -‐ black string phase transi1ons.
• Confinement, chiral symmetry breaking and the dynamics of gauge theories, non-‐ rela1vis1c limits of field theory,
Lifshitz scaling, RG flows, phase diagram of gauge theories in low dimensions at large N.
• New formula1ons for string dynamics, matrix theory, low-‐dimensional string vacua.
• The study of nonsupersymmetric strong weak coupling duali1es in quantum field theories in three dimensions,
and the rela1onship to anyonic sta1s1cs.
Members: Gautam Mandal Shiraz Minwalla Sandip Trivedi
4dYM
AdS D4 soliton
Black D4
IIA SUGRA
SS transition
confinement phase
confinement/deconfinement phase transition in 4dYM.deconfinement phase
W0≠0
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W4≠0
W4≠0
W0≠0
W4≠0
W0=0
AdS -SYM Phase diagram
