Colloquia

Extra dimensions of space might be present in our universe. If so, we want to know 'How do dimensions hide?' and 'Why are three dimensions special?' I'll give potential answers to both these questions in the context of localized gravity.



Organiser(s): L. Alvarez-Gaume / PH-TH

Note: * Tea & coffee will be served at 16:00.

Talk is broadcasted in Council Chamber.

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For more than three decades, the quest for ever higher precision in laser spectroscopy of the simple hydrogen atom has inspired many advances in laser, optical, and spectroscopic techniques, culminating in femtosecond laser optical frequency combs  as perhaps the most precise measuring tools known to man. Applications range from optical atomic clocks and tests of QED and relativity to searches for time variations of fundamental constants. Recent experiments are extending frequency comb techniques into the extreme ultraviolet. Laser frequency combs can also control the electric field of ultrashort light pulses, creating powerful new tools for the emerging field of attosecond science.

Organiser(s): L. Alvarez-Gaume / PH-TH

Note: * Tea & coffee will be served at 16:00..

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The axion provides a solution to the strong CP problem and is a cold dark matter candidate. I will review the limits on the axion from particle physics, stellar evolution and cosmology. The various constraints suggest that the axion mass is in the micro-eV to milli-eV range. In this range, axions contribute significantly to the energy density of the universe in the form of cold dark matter. Dark matter axions can be searched for on Earth by stimulating their conversion to microwave photons in an electromagnetic cavity permeated by a strong magnetic field. Using this technique, limits on the local halo density have been placed by the Axion Dark Matter experiment at Lawrence Livermore National Laboratory. I will give a status report on ADMX and its upgrade presently under construction. I will also discuss the results from solar axion searches (Tokyo helioscope, CAST) and laser experiments (PVLAS)..

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What do physicists want to discover with experiments at the LHC? What is the Higgs boson? What are the new phenomena that could be observed at the LHC?
I will try to answer these questions using language accessible also to non-experts.


Organiser(s): L. Alvarez-Gaume / PH-TH

Note: * Tea & coffee will be served at 16:00..

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The high oil price and warnings by the international energy agencies about possible oil and gas supply disruptions have brought the energy question back to headline news. While facts about the world's energy use and the different energy resources are easily available, the debate about the energy problem is, even within the scientific community, dominated by many myths, folktales and even fairytales.

This talk confronts these fantasies with the physics laws and facts about our energy sources and their use. Scenarios for the future of the industrialized and the so-called developing world are confronted with today's scientific understanding of the energetic 'limits of growth'.

Are we approaching the natural limits? And if so what consequences can be imagined for our energy-intense societies?


Organiser(s): L. Alvarez-Gaume / PH-TH

Note: * Tea & coffee will be served at 16:00..

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With the ESO Very Large Telescope, Europe has acquired a ground-based observational optical/IR facility, which is second to none in the world. Seven years of science operations with the 8.2-m Unit Telescopes have brought an outstanding harvest of scientific breakthroughs and more than 1,000 refereed papers have been published by its users. Moreover, the VLT Interferometer has now become a much appreciated mature facility that has provided outstanding results. The talk will describe some of the research highlights, based on the unique capabilities of the VLT/VLTI, and offers a glimpse of research possibilities to come with the future ESO facilities..

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The semi-classical birth of the Universe.

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The semi-classical birth of the Universe.

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Professor C.N. Yang is a living legend in Physics. The depth and breadth of his contributions are simply staggering. He is at the origin of the discovery of parity violation, Yang-Mills theory (with which we write the basic interactions in the standard model), the Yang-Baxter equation in the theory of integrable systems, the applications of topology in physics, and a long etcetera. He is also an excellent speaker. It is rare to have people of his stature come and visit CERN. It will be a memorable colloquium..

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One of the most fundamental and far-reaching advances in modern physics was the introduction of spinors by Dirac and their use in his famous equation. I will trace back the origins of this to William Rowan Hamilton's discovery of quaternions and follow up with a survey of the use of spinors in physics and mathematics. Despite their undoubted success the real meaning of spinors remains elusive..

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The existence of cosmic rays with energies in excess of 10²⁰ eV represents a longstanding scientific mystery. Unveileing the mechanism and source of production/acceleration of particles of such enormous energies is a challenging experimental task due to their minute flux, roughly one km² century.

The Pierre Auger Observatory, now nearing completion in Malargue, Mendoza Province, Argentina, is spread over an area of 3000 km². Two techniques are employed to observe the cosmic ray showers: detection of the shower particles on the ground and detection of fluorescence light produced as the shower particles pass through the atmosphere. I will describe the status of the Observatory and its detectors, and early results from the data recorded while the observatory is reaching its completion.

Organiser(s): L. Alvarez-Gaume / PH-TH

Note: * Tea & coffee will be served at 16:00..

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All modern theories for particles, forces and even space-time itself, use the framework provided by quantum mechanics. The Standard Model is a quantized field theory. Even superstring theory is based on quantum mechanics. There is something odd about quantum mechanics: it brilliantly allows us to predict the outcome of experiments, yet it gives confusing statements about what really is going on inside particles and fields. Suppose we would be asking for a theory that allows us to describe what actually happens in less ambiguous terms, without destroying the magnificent successes of quantum mechanics, would this help us to answer some of the great mysteries of theoretical elementary particle physics?

Organiser(s): L. Alvarez-Gaume / PH-TH

Note: * Tea & coffee will be served at 16:00..

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