Study of the string theory landscape seems now to have become the hot research topic that one should be working on in order to be taken seriously as a cutting-edge researcher in particle theory. Last week there was a workshop at Trieste on String Vacua and the Landscape that drew many researchers. Some of the talks from the workshop are available on-line.
Following on the heel’s of Susskind’s popular book promoting the landscape, which has received excellent reviews from particle and string theorists, there’s a new one on the same topic coming out later this month from cosmologist Alex Vilenkin, entitled Many Worlds in One: The Search for other Universes.
As string theorists in search of something to write papers about pour into the landscape, with its more than 10500 possible hot research topics to work on, Sean Carroll reports from a cosmology workshop at the Perimeter Institute that trouble may be ahead for the subject. Sean gives a short summary of the talks at the workshop, in the majority of cases ending with “Made fun of the landscape”, or “Made fun of the anthropic principle”.
The main argument for the landscape mania has always been that it justifies Weinberg’s “prediction” of the size of the cosmological constant. I’ve written elsewhere about why this is not a legitimate scientific prediction, and is off by at least an order of magnitude anyway. Evidently Steinhardt and Turok are about to put out a paper claiming that the situation is much worse than this, that if you take anthropic reasoning seriously, the natural “prediction” of the landscape is that:
the cosmological constant should be quite large (many times the matter density, although presumably not at the Planck scale), and we should live in a single lonely galaxy in an empty universe dominated by vacuum energy.
It will be interesting to see if landscapeologists will be willing to admit that the only supposed “prediction” of this subject doesn’t work at all, and that it is not only pseudo-science, but failed pseudo-science.
All of this just goes to demonstrate the truth of the maxim “Physics is an experimental science”. There’s just no data beyond the SM (from cosmology there’s dark matter and dark energy, but one cannot do controlled expts as a function of pressure and temperature etc, or produce particles of dark matter to measure decay cross-sections and branching ratios, for example). Ultimately, there has to be some data beyond SM (but nobody knows when/where this will happen). Until then theoretical speculation will just pile on speculation.
Steinhardt and Turok are serious people. This is very interesting news.
Does this mean that Lenny will be joining “the other side”…?
–
Steinhardt and Turok finally discovered the runaway effect, or what?
sunderpeeche Says:
There’s just no data beyond the SM (from cosmology there’s dark matter and dark energy […]
There is dark matter, there is dark energy, there are neutrino masses, there is the horizon-/ homogeneity/ flatness-problem, the matter-antimatter asymmetry, there are a whole collection of astrophysical mysteries (e.g. the ‘axis of evil’, the GZK-cutoff, and the Pioneer anomaly (the latter two, I should add, I don’t believe in)), then there are the well-known mysteries within the SM: the hierarchy-problem, the values of the Yukawa-couplings, EWSB, family symmetries, etc. If you ask me, we have plenty of data beyond standard, even though not from collider physics. It’s the theorists side that has to catch up.
Best, B.
As string theorists in search of something to write papers about pour into the landscape, with its more than 10^500 possible hot research topics to work on, Sean Carroll reports from a cosmology workshop at the Perimeter Institute that trouble may be ahead for the subject. Sean gives a short summary of the talks at the workshop, in the majority of cases ending with “Made fun of the landscape”, or “Made fun of the anthropic principle”.
Not sure that is a good development. I’d rather see the topic die silently, and vanish into nirvana.
I remember last summer I was on a conference where a student gave a talk about some class of string-models whose properties he had made statistics about. He had a selection of about 800 of these models, he said.
The next speaker was HP Nilles, who mentioned the previous talk, and then remarked very dryly that this means, it would take him only 10^ four hundred-something grad. studs to scan the whole landscape 😉
Best, B.
The 2006 Simons Workshop in Mathematics and Physics will have as one of its main focus the Landscape topic. This workshop will take place at Stony Brook University.
http://insti.physics.sunysb.edu/itp/conf/simonswork4/
sunderpeeche said “… there’s dark matter and dark energy, but one cannot do controlled expts …”.
Actually, there is one controlled dark energy experiment now under way, by P A Warburton of University College London. It is EPSRC Grant Reference: EP/D029783/1, “Externally-Shunted High-Gap Josephson Junctions: Design, Fabrication and Noise Measurements”, starting 1 February 2006 and ending 31 January 2009 with £ Value: 242,348. Its abstract states in part:
“… A possible source of this dark energy is vacuum fluctuations which arise from the finite zero-point energy of a quantum mechanical oscillator, hf/2 (where f is the oscillator frequency). … A recent publication by Beck and Mackey … suggests the possibility that dark energy may be measured in the laboratory using resistively-shunted Josephson junctions (RS-JJ’s). Vacuum fluctuations in the resistive shunt at low temperatures can be measured by non-linear mixing within the Josephson junction. If vacuum fluctuations are responsible for dark energy, the finite value of the dark energy density in the universe (as measured by astronomical observations) sets an upper frequency limit on the spectrum of the quantum fluctuations in this resistive shunt. Beck and Mackey calculated an upper bound on this cut-off frequency of 1.69 THz. … We therefore propose to perform measurements of the quantum noise in RS-JJ’s fabricated using superconductors with sufficiently large gap energies that the full noise spectrum up to and beyond 1.69 THz can be measured. … By performing experiments on both the nitrides and the cuprates we will have two independent measurements of the possible cut-off frequency in two very different materials systems. This would give irrefutable confirmation (or indeed refutation) of the vacuum fluctuations hypothesis. …”.
I am aware that there exist no-go type theoretical objections to the work of Beck and Mackey, but it is interesting to me that experiments are under way to answer the question experimentally, thus effectively testing the assumpions of the no-go theoretical objections.
Note that Warburton sees his experiment as worthwhile whichever way ( confirmation or refutation of Beck and Mackey ) it turns out.
Tony Smith
http://www.valdostamuseum.org/hamsmith/
If the data from Lund Observatory in Sweden by professor Sveneric Johansson and his PhD student Maria Aldenius in collaboration with Dr Michael Murphy, Cambridge, UK means change in fundamental constants, I wonder how one can “explain” changes in fundamental constants in terms of our universe following a particular trajectory through the multiverse/superspace landscape of all possible universe with fixed fundamental constants? What are the constraints on such trajectories? Do either landscaper or stringers answer these foundational questions? Are such explanations consistent with the April 21 this year findings published in Physical Review Letters implying that a dimensionless constant – the ratio between the electron mass and the proton mass – has changed with time?
Variable Physical Laws
http://www.sciencedaily.com/releases/2006/06/060609122206.htm
Surely if The Landscape makes a wrong prediction it stops being pseudo-science and just becomes failed science?