Our Team

Mikhail Kapranov

Research Field: Mathematics

Professor

My research is in the areas of algebra, algebraic
geometry and category theory. These areas are
the source of powerful conceptual tools forunderstanding the concept of space in a wide sense,from very classical to very abstract.
For example, the classical subject of hypergeometricfunctions was developed (in my joint works withI.M. Gelfand and A .V. Zelevinsky) to include period
integrals of algebraic hypersurfaces in toric varieties.
This led us to the discovery of secondary polytopes,
which are combinatorial geometric objects governing
both hypergeometric functions and discriminant
polynomials in singularity theory. These concepts are
now widely used in Mirror Symmetry.
Other directions of algebraic geometry which I
am interested in (and have worked) include noncommutative geometry (study of the neighborhood

Shamik Banerjeeof the commutative regime), derived and infinitedimensional geometry (algebro-geometric study ofspaces of formal loops and paths).
Category theory provides a unified background for
all these areas. In addition, various flavors of category
theory (triangulated categories, higher categories,
theory of operads) lead to contexts where algebraic
expressions themselves become objects with nontrivial geometric structure, not really expressible ona (1-dimensional) line. This additional interface ofalgebra and geometry seems necessary in order toapproach truly higher-dimensional problems.

Research Field: Theoretical Physics

Postdoc

My main research interest is string theory and field
theory. My recent work focuses on entanglement
entropy. Entanglement entropy has applications inmany branches of physics starting from black holes
to quantum critical phenomena. It is also an emerging
tool in field theory. I am trying to develop new nonperturbative techniques for calculating entanglement
entropy in field theory. I am also interested inholographic, or, more precisely, AdS-CFT duality. It

12gives us a host of exact results for entanglement
entropy, and one of the motivations for developing
new techniques is to explain these results from thefield theory side.

Kavli IPMU News No. 26 June 2014

Christophe Bronner

Research Field: Experimental Physics

Postdoc

My research focuses on the experimental study ofneutrinos, and more particularly on the phenomenonof neutrino oscillations, where a neutrino produced
in a given flavor can be later observed to interact asa neutrino of another flavor. This phenomenon could
also violate CP symmetry, in which case neutrinos
and anti-neutrinos would oscillate differently.
Most of my work has been done in the Tokai
to Kamioka (T2K) experiment, in which a beam ofmuon neutrinos is produced in the J-PARC centeron the East coast of Japan and sent to the Super-

Yohsuke Imagi

Kamiokande detector in the Gifu prefecture to studyneutrino oscillations. I have been working on thenear detectors construction and operation, as wellas on analysis of T2K data to measure some of theparameters of the PMNS model, describing neutrinooscillations.

Research Field: Mathematics

Postdoc

I am studying special Lagrangian geometry, an areaof differential geometry. For Yang-Mills instantons
in dimension 4 and pseudo-holomorphic curves, we
already have a good understanding of singularities,
and we can define a nice compactification of moduli
spaces, which is a source of interesting mathematics
and physics. One may want to do somethingsimilar for special Lagrangian submanifolds, but
their singularities seem considerably more difficult
to analyze than those of Yang-Mills instantons
in dimension 4, or those of pseudo-holomorphic

Hironao Miyatake

curves. So we have not yet achieved a nicecompactification of the moduli space of special
Lagrangian submanifolds. I am developing a
deep theory on simple singularities, using sometechniques from geometric measure theory and
Lagrangian Floer theory.

Research Field: Cosmology

Our Team

Postdoc

I am interested in what the acceleration of theUniverse indicates in the context of fundamental
physics. I have been working on reconstructing thedistribution of dark matter by analyzing the weaklensing effect on imaging data. What I would liketo accomplish at the Kavli IPMU is to measure thematter distribution of an even larger volume throughdata taken by the Hyper Suprime-Cam Survey thatstarted from March 2014, and to constrain the natureof dark energy and test gravity theory based on thismass distribution.

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Koichi Nagasaki

Research Field: Theoretical Physics

Postdoc

I was working on string theory and supersymmetricfield theories. Now I am interested in the AdS/CFT
correspondence which is thought to be a useful tool
for studying unknown properties of string theory.
Recently I was studying a certain class of operators
called non-local operators. I proposed their gravity
duals and showed complete agreement between
gauge and gravity theories.
Recently, I am considering a system consisting ofD3 branes and probe D-branes. This system gives

Natsumi Nagata

a special gauge theory which contains defects
or boundaries. Using this system, I am thinkingof revealing relations between these non-local
operators and brane configurations.

Research Field: Theoretical Physics

Postdoc

My current research interest is to study thephysical observables which are sensitive to physics
beyond the Standard Model. In particular, I havebeen focusing on the direct searches of dark matter,the measurements of the electric dipole moments,
and the proton decay experiments, and developed
the method of evaluating the contribution of new
physics to the corresponding physical quantities. Suchan approach based on the precision measurements
can be complementary to the collider searches, andRio Saitouin fact the most promising when the scale of newphysics, such as supersymmetry, is somewhat higher
than the electroweak scale, as is suggested by thenull result at the early stage of the LHC running.

Research Field: Cosmology

Postdoc

I aim to reveal the whole cosmic history from thebeginning to the present day or the future. People
believe that in the early universe, the universe
had experienced the accelerated expansion called
inflation, and the present universe is also accelerated
by dark energy. We must make these phenomena
clear. With this in mind, I investigated the modelswhich unify the inflation and late-time acceleration.
Now, Iʼm interested in the details of the gravitational

14wave created during inflation and the effect of thevacuum expectation value of the Higgs particle on
the evolution of the universe.

Kavli IPMU News No. 26 June 2014

Hiroshi Takano

Research Field: Theoretical Physics

Postdoc

I am studying about the phenomenology ofneutrino and dark matter. These problems can be
explained in TeV energy scale new physics, which isaccessible by experiments in the near future. Recently,I am interested in the production scenarios of dark
matter particles, thermal or non-thermal relics, coldor warm, and so on. I am trying to understand these

Yasuhiro Takemoto

scenarios and their general behavior.

Research Field: Experimental Physics

Postdoc

How has this universe been formed? Neutrinos,
one of the elemental particles, are an important
probe for this question. Due to their extremely
small cross section, neutrinos have provided us withdirect information inside the sun or the earth. The
possibility that neutrinos are Majorana particles
further gives clear explanation of the current matterdominant universe. I have been studying the universe
using neutrinos in the KamLAND and KamLAND-Zen

Alexey Tolstov

experiments. At the Kavli IPMU, I will continue thisresearch and also I will start dark matter search using
KamLAND.

Research Field: Astrophysics

Postdoc

The key issue around which my research interests
are constructed is a question of understanding
the mechanisms of supernova explosion andthe origin of gamma-ray bursts based on theanalysis of observational data: spectra and light
curves. Numerical modeling of non-equilibrium
radiative and hydrodynamic processes in expanding
supernova envelopes provides me the ability tostudy nucleosynthesis signatures in the opticallight curves and spectra of faint supernovae, theOur Teamorigin of extremely metal poor stars, and supernova
shock breakout phenomenon for mildly relativistic
ejecta. All of this helps to answer on some pressing
questions of stellar evolution and cosmology.

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