May 08

When: Tuesday, May 8, 2018, 2:30 pm

Location: MPQ Garching, New Lecture Hall, Room B 0.32

M.Sc. Lothar Maisenbacher (PhD, Emeritus Group Laser Spectroscopy) and Dr. Antoine Tilloy (PostDoc, Theory Division) will give a talk about

"Precision spectroscopy of atomic hydrogen and the proton radius puzzle" (L. Maisenbacher) and "Does gravity have to be quantum?"

**Abstracts:**

**Precision spectroscopy of atomic hydrogen and the proton radius puzzle** (M.Sc. L. Maisenbacher)

*more information will follow soon*...

**Does gravity have to be quantum? (**Dr. Antoine Tilloy)

*Theoretical physicists have been restlessly trying to quantize gravity, leveraging more and more elaborate methods in the last 50 years. But is this even needed? Could gravity not just be classical at the fundamental level? Surprisingly, this possibility is still open. It is not forbidden by known experimental results nor by theoretical arguments (although some pseudo "no-go" theorems have historically been proposed). Interestingly, the implications of the quantum or classical nature of gravity are best discussed in the Newtonian limit and there is no need to go to general relativity to understand what is at stake. After critically discussing the historical arguments in favor of the quantization of gravity, I will present simple Newtonian models (with a quantum optics intuition), in which a fundamentally classical gravitational force cohabits with quantum matter. Free of conceptual paradoxes and so far not experimentally falsified, these models make the classical gravity option at least defensible. Fortunately, although separating different approaches to quantum gravity may forever be out of experimental reach (requiring ludicrously large accelerators), discriminating between semiclassical and fully quantum models seems doable in the near future; and only with table top experiments. *

**Despite what the title might suggest, this talk will require absolutely no prior familiarity with quantum gravity and rely only on elementary non-relativistic quantum mechanics**.*

**For more information visit the MPQ weppage. **

Get MPQ Colloquium: Precision spectroscopy of atomic hydrogen and the proton radius puzzle / Does gravity have to be quantum? event as calendar entry.