The Institute for Theoretical Physics offers the following seminars:
Muonic hydrogen, a proton orbited by a negative muon, is one of the most basic atomic systems. A few years ago, we have measured the Lamb shift in muonic hydrogen (energy difference between 2S and 2P states) with infrared laser spectroscopy in a pioneering experiment at the Paul Scherrer Institute (PSI). Combined with QED calculations we determined the proton radius (root-mean-square charge radius). Our value is 4% smaller and deviates significantly from the previous values from electron-proton scattering and hydrogen spectroscopy. This discrepancy in a basic field of particle physics created a lot of theoretical investigations and initiated new experiments, but the "proton radius puzzle" is still unsolved today. I will give an overview about the present status, including new data from muonic deuterium and helium.
ETH Science City HPV G 4 - Wed 27.05.2015 16:15
Colloidal nanocrystals are crystals of semiconductor 2-12 nanometers in diameter that are grown in rapid, solution-based chemical reactions. They have recently found commercialization in TV displays and are of promise for solar cells due to their ability to be manufactured at low-cost and their attractive optical properties, such as size-dependent bandgaps. This talk presents recent work using electronic, optical, and neutron spectroscopies along with ab initio and empirical simulations that has yielded insights into the mechanisms at play in these quantum systems and ways they can be engineered to obtain higher performance materials and devices.
ETH Science City HPV G 4 - Wed 20.05.2015 16:15
It has recently been suggested by Strominger and collaborators that the soft theorems for Yang-Mills and gravity amplitudes can be interpreted as Ward identities of a 2d CFT at null infinity. In this talk, I will derive the soft theorems using a 2d CFT known as ambitwistor string theory, which describes 4d Yang-Mills and gravity with any amount of supersymmetry. I will also describe how the algebra of soft limits can be encoded in the braiding of soft vertex operators, and compute 1-loop corrections to the subleading soft graviton theorem by considering ambitwistor string theory on a genus one worldsheet.
ETH Science City HIT E 41.1 - Wed 13.05.2015 11:30
ETH Science City HIT E 41.1 - Tue 12.05.2015 11:15
Periods are the complex numbers which may be defined by integrals of algebraic functions (with rational coefficients) over domains defined by algebraic inequalities (with rational coefficients). They include all algebraic numbers. The philosophy of motives predicts that classical Galois theory for algebraic numbers is a special case of a Galois theory for periods. In this talk we will introduce a family of periods, called dissection polylogarithms, indexed by some combinatorial objects, called dissection diagrams, and show that their Galois theory is encoded in a combinatorial Hopf algebra. This generalizes Goncharovs work on (generic) iterated integrals on the punctured complex line. No a priori knowledge of the theory of motives is required.
ETH Zentrum HG G 43 - Thu 7.05.2015 15:15