Trinity 2011

When? Where?

Talks are held at 8:15pm on Thursday evenings (unless otherwise stated) in the Lindemann Lecture Theatre of the Clarendon Laboratory

Cost: Free for members, £2 for non-members
Life Membership £8

What’s on this term?

Thursday 1st Week – Social – 8pm King’s Arms
This week, to welcome you all back into the swing of things, we’re having a pub trip. We’ll Start at the King’s Arms and go from there. Our Trinity pub trips are a great time to chill out with ‘normal’ physicists where the conversation is broadly in two categories: anything physics and anything-but physics.

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First round on us!
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Thursday 2nd Week – Dr Todd Huffman
“The Mysterious Bump in the CDF Data”

Could this mark a change in particle physics as we know it?.. Maybe:

The CDF experiment recently published a result which looked that the decay of W bosons to two quarks, which produces two jets of particles in their detector. In the course of looking at this decay they reported seeing another excess of events around 140 GeV/c^2 in mass. This peak hit the press in a big way last month because, if it were to be confirmed, would represent a particle that has completely escaped the Standard Model of fundamental interactions. It would have to be a fundamental particle which ONLY had a colour charge and which, further, does not decay into leptons. No such beast exists even among speculative theories such as Supersymmetry.

I will discuss this result and then talk about how discoveries are made at these large experiments, how we can make mistakes, and how that, even if we do not make mistakes and are careful…sometimes it just doesn’t matter.


Thursday 3rd Week – Prof. Ofer Lahav (UCL)
“Light and Darkness in the Accelerating Universe”

It seems we live in a bizarre Universe. One of the greatest mysteries
in the whole of science is the prospect that 75% of the Universe is
made from a mysterious substance known as ‘Dark Energy’, which causes
an acceleration of the cosmic expansion. Since a further 21% of the
Universe is made from invisible ‘Cold Dark Matter’ that can only be
detected through its gravitational effects, the ordinary atomic matter
making up the rest is apparently only 4% of the total cosmic budget.
These discoveries require a shift in our perception as great as that
made after Copernicus’s revelation that the Earth moves around the
Sun. The lecture will start by reviewing the chequered history of
Dark Energy, not only since Einstein’s proposal for a similar entity
1917, but tracing the concept back to Newton’s ideas. The lecture
will summarize the current evidence for Dark Energy and future
surveys in which UK astronomers are heavily involved: the “Dark Energy Survey”,
the Hubble Space Telescope and the proposed Euclid space mission.


Thursday 4th Week – Prof Tony Kent
“Superlattice saser: sound amplification by the stimulated emission of radiation at terahertz frequencies”

Sound amplification by the stimulated emission of radiation (saser) is the acoustic
analogue of the laser. Sasers would provide an intense source of coherent
acoustic waves which may be used in acoustic spectroscopy and imaging. The
two key elements of a saser are a medium having acoustic gain and a cavity to
confine phonons and so provide acoustic feedback. In this talk I will describe
THz saser devices in which both the gain and confinement are provided by
multi-layered semiconductor nanostructures known as superlattices (SLs). I will
explain how the particular electronic properties of SLs can give rise to phonon
amplification (acoustic gain) due to a phonon-stimulated quantum cascade of
electrons through the structure. I will also explain how SLs can be used to make
acoustic Bragg mirrors which are used to confine phonons in a cavity. Recent
experimental results providing the evidence for saser action in the devices will be
presented.


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