Sommerfeld Theory Colloquium (ASC)

Sommerfeld Theory Colloquium, We review the current status of measurements of the spectrum, an isotropy and polarization of the CMB, and their impact on cos-

mology. We show that there is still a large discovery potential in

these measurements, complementing and synergic to other cosmology observations. We also describe a selection of new measurement eff�orts, including high precision measurements of CMB polarization

with ground-based, stratospheric balloon and satellite experiments,

focusing on the astrophysical and technological limits of these measurements.

Sommerfeld Theory Colloquium, I will review the basic defi�nitions and ideas of the twistor program

for fundamental physics, as started by Roger Penrose around 1970. I

will give particular attention to certain conformally invariant struc-

tures involving deformed helicities, relevant to scattering amplitudes

for massless �elds. These played a role in Penrose's earliest contour

integral expressions, but have more recently been rediscovered and

greatly developed as an approach to regularization.

Sommerfeld Theory Colloquium, Remarkably, a strong candidate for Dark Matter exists within the Standard Model. Theoretical arguments suggest that QCD forces in the flavor-singlet sector may be strong enough that the H-dibaryon is a deeply-bound, compact state which is absolutely stable with a mass < 2mp. This possibility has gotten recent support from lattice QCD studies, which – although not yet at high enough resolution and sensitivity to confront the hypothesis – show a deeper binding than other states. As I will show, reasonable assumptions about the H’s mass and wave function lead to the observed dark matter density and DM-to- (3-quark) baryon ratio. I will discuss why H-DM is not excluded by the various experimental and observational limits, and discuss what its observational signatures would be.

Sommerfeld Theory Colloquium, To pinpoint the microscopic mechanism for superconductivity has

proven to be one of the most outstanding challenges in the physics of

correlated quantum matter. Thus far, the most direct evidence for

an electronic pairing mechanism is the observation of a new symmetry

of the order-parameter, as done in the cuprate high-temperature

superconductors. Like distinctions based on the symmetry of a locally

defi�ned order-parameter, global, topological invariants allow for

a sharp discrimination between states of matter that cannot be transformed

into each other adiabatically. Here we propose an unconventional

pairing state for the electron

uid in two-dimensional oxide

interfaces and establish a direct link to the emergence of nontrivial

topological invariants. Topological superconductivity and Majorana edge states can then be used to detect the microscopic origin for

superconductivity. In addition, we show that also the density wave

states that compete with superconductivity sensitively depend on the

nature of the pairing interaction. Our conclusion is based on the special

role played by the spin-orbit coupling and the shape of the Fermi

surface in SrTiO3/LaAlO3-interfaces and closely related systems.

Sommerfeld Theory Colloquium

Sommerfeld Theory Colloquium, The role of Type Ia supernovae in observational cosmology has evolved

from being ”avant-garde” in the early 1990’s until today’s mature status of precision cosmology. Several large transient surveys have been detecting supernovae routinely, near and far, with the aim of probing what is causing the accelerated expansion of the Universe.

With time, the focus has changed towards addressing the intricacies of astrophysical effects that could bias the fits of cosmological parameters,

most notably the nature of dark energy. In this talk, aimed at high-energy physics theorists(!), I will try to convey the status of

the field, high-lighting some progress and set-backs, based on studies

of the closest Type Ia SN in modern time that exploded in the

beginning of 2014 in the near-by galaxy M82.

Sommerfeld Theory Colloquium, Various aspects of lattice gauge theory will be briefly discussed including, general principles, sources of systematic errors, dynamical fermions, QCD phenomenology, the FLAG project and, if time allows, some applications of lattice theory to other non-perturbative BSM phenomena.

Sommerfeld Theory Colloquium, The conjectured relation between higher spin theories on anti de-Sitter (AdS) spaces and weakly coupled conformal �field theories is reviewed. I shall then outline the evidence in favour of a concrete duality of this kind, relating a speci�c higher spin theory on AdS3

to a family of 2d minimal model CFTs. Finally, I shall explain how

this relation �ts into the framework of the familiar stringy AdS/CFT correspondence.

Sommerfeld Theory Colloquium, Equivalence principle violation, deviations from the inverse-square

law of gravity, and long-range interactions between particle spins

o�er powerful tests of beyond-the-standard-model physics. Using a

torsion pendulum, a technique that dates to the 18th century, is still

the most sensitive way to search for these signatures of new physics.

I will talk about how the experiments are done and give an update on the current and future status of such torsion balance experiments in the Eot-Wash group.

Sommerfeld Theory Colloquium, Several new techniques are currently being employed to probe the strong gravitational fi�eld in the vicinity of black holes. Long baselineinterferometry at sub-millimeter wavelengths sets constraints on the

silhouette of the black holes in the Galactic center (SgrA*) and M87.

Stars which get tidally disrupted as they orbit too close to a single

black hole are being discovered at cosmological distances. Electromagnetic counterparts of black hole binaries in galaxy mergers are being identifi�ed, and can be used to calibrate the rate of gravitational wave sources. Most interestingly, the recoil induced by the

anisotropic emission of gravitational waves in the �nal plunge of binaries leaves unusual imprints on their host galaxies. Finally, the

lecture will describe new constraints on the contribution of primordial black holes to the dark matter.