Comments on: Interim Roadmap Report

By: Mark

Mark — Mon, 10 Jul 2006 23:59:49 +0000

Hi Shantenu,

I agree with you, although HEPAP isn’t the right forum for that. NASA used to have a nice little program doing some of the things you’re mentioning, but recent cuts have decimated it. I wrote about this a little while ago, if it is useful at all

http://blogs.discovermagazine.com/cosmicvariance/2006/05/22/from-quantum-to-cosmos-i/

By: Shantanu

Shantanu — Mon, 10 Jul 2006 21:40:04 +0000

Hi
Joanne,
I would like to add to something to what Tony said.
Besides these astrophysical experiments in searching for dark energy, there should be more
experimental tests of fundamental gravity (such as precision tests of EEP, lunar laser ranging tests of strong equivalence principle, tests for deviation from Newton’s law at small
distances, high precision ‘COW’ [Collela-Overhause-Werner] experiments, testing the
gravitational force on antimatter , testing if Pioneer anomaly is correct and so on.
Of course not all these experiments may not solve the dark energy problem. But if dark energy
is really due to “modified gravity”, why not design/invest in laboratory based experiments
to test/probe gravity more precisely. (note that there is a also a tiny community of physicists
who believe that “dark matter ” could also be due to modified gravity) . this way we could at least rule out modified gravity as amn explanation. But of course
it is possible that all the experiments which I mention do not come under the purview of
HEPAP.

By: Tony Smith

Tony Smith — Mon, 10 Jul 2006 21:34:56 +0000

graviton383 said “… Beck’s idea for any Dark Energy measurement has run into a number of troublesome issues; see Moran & Jaeckel in astro-ph/0605711 and their Refs. 2-5. …”.

To the extent that the “troublesome issues” are in the form of No-Go theorems:

the way to resolve whether or not Beck’s idea is valid is NOT to have debates about No-Go theorems (a lot of interesting physics has come about by regarding No-Go theorems, not as signals to give up, but as telling us to ask which of their assumptions need to be changed in order to evade them – for example, the use of Lie superalgebras to evade Coleman-Mandula No-Go restrictions on constructions with ordinary Lie algebras);

but

the way to resolve whether or not Beck’s idea is valid IS to DO EXPERIMENTS AND SEE WHAT HAPPENS.

That is what Warburton is doing, and maybe it will show that Beck’s ideas are correct, maybe it will indicate what types of superconductors should be used, and maybe it will show that Beck’s ideas are wrong,
but
whatever the results, they are guaranteed to be interesting,
and
cheap (less than 1/40 of the $20 million threshold for HEPAP to even consider it.

If (long shot) Beck turns out to be correct and Warburton shows how to control Dark Energy, then it is fair to hope (but not guaranteed) that people will use Dark Energy for constructive purposes.

Tony Smith
http://www.valdostamuseum.org/hamsmith/

By: Quasar9

Quasar9 — Mon, 10 Jul 2006 17:32:53 +0000

Hi Graviton383, I think you missed the point of the question.
The Question was not whether Dark Energy exists (or not) in Space, but whether the US military might be working on creating Dark Energy on Earth. As for dark energy existing in space – well let us open this can of worms – what do you call dark energy?, the forces of the evil Empire: Darth Vader in the Dark Star, or maybe even a blackhole that syphons garbage from this universe into a parallel one – you know incinerator style, or much much more like the tornadoes which clean any pollution on their path across the US, you know vaccum cleaner style, and throw cows, pigs, and even fish on some other part of the farm, state or planet or even ‘parallel’ world.

PS – Do Nuclear warheads count as dark energy producers?
PPS – Never mind anti-matter, can anti-gravity be produced, and I don’t just mean conventional rocket or Space Shuttle propulsion systems

By: graviton383

graviton383 — Mon, 10 Jul 2006 15:47:41 +0000

Tony and Quasar9:

Apparently Beck’s idea for any Dark Energy measurement has run into a number of troublesome issues; see Moran & Jaeckel in astro-ph/0605711 and their Refs. 2-5.
It seems that this is not what we are after in a Dark Energy measurement..Of course we should all be reminded, as Sean will tell us, that it is not obvious whether or not Dark Energy (as a new form of matter) exists and even if it does it may be unrelated to the cosmological constant or the `vacuum energy’ of ordinary field theory.

By: Quasar9

Quasar9 — Mon, 10 Jul 2006 13:06:14 +0000

Though of course I hope all Dark Energy is related to Astro Physics whether its $20.oo or $20million projects. Imagine letting your military walk around loose with that kinda energy on Earth. lol!

By: Quasar9

Quasar9 — Mon, 10 Jul 2006 12:27:05 +0000

Well JoAnne comments like your lastone certainly cup up on my ‘radar’
However, I feel you were a little dismissive to Tony’s query. After all increase the budget by a magnitude of 40 and the question would read:
“Is there any USA interest in non-astrophysical Dark Energy experimental work”?
Have a nice day! as they say in the USA!

By: JoAnne

JoAnne — Mon, 10 Jul 2006 04:58:09 +0000

Tony,

I am not aware of any such projects in the US, but let me preface this comment with the remark that our committee is only charged at looking at experiments that cost $20 Million or more. Anything as inexpensive as you mention is way below our radar screen.

By: Tony Smith

Tony Smith — Mon, 10 Jul 2006 01:30:21 +0000

JoAnne, with respect to Dark Energy experiment/observation, you mention “… supernova surveys, baryon acoustic oscillations, weak lensing, and cluster surveys …”. Those proposals seem to all be astrophysical in nature.

Is there any USA interest in non-astrophysical Dark Energy experimental work such as the Josephson Junction experiment recently begun by Warburton in London?

It is 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 Â£ Value: 242,348 ?

Roughly it is based on Christian Beck’s idea (see astro-ph/0512327 ) that If vacuum fluctuations are responsible for Dark Energy then Josephson Junctions might detect and study it.

For details of Warburton’s experimental work, see the web page at
http://gow.epsrc.ac.uk/ViewGrant.aspx?GrantRef=EP/D029783/1

Isn’t it the kind of thing that might have such a high payoff that it is worth a gamble (especially if the cost is less than half a million US dollars) ?
Even a negative result would be useful, as it would rule out some types of Dark Energy models.

Tony Smith
http://www.valdostamuseum.org/hamsmith/

By: JoAnne

JoAnne — Sun, 09 Jul 2006 19:58:21 +0000

Nigel,

There are a variety of ways to measure the variables which parameterize dark energy: supernova surveys, baryon acoustic oscillations, weak lensing, and cluster surveys. From ground-based experiments or space-based experiments. Each technique is at a different stage of development (proven ability) and each has different features in terms of the precision with which it measures the parameters. Our job is to figure out which experiment(s) gives the best measurement of the parameters at an affordable cost. It’s tricky.

On the theoretical side, I think it’s safe to say that it’s fair game in explaining the source of dark energy. Many different options are being explored. We need the next generation of experiments to learn more.

There is a very nice Dark Energy Task Force report (sponsored by HEPAP) that was summarized by Risa.