Can we be sure that decay times are constant?

[Duda Jarek]

Particle decay is clearly some statistical process. Generally speaking, particles are some stable solutions of some physics (like a field theory) - they are some local/global energy minimums for given constrains like spin or charge.

So from energetic point of view, particle decay should be getting out of some local energy minimum by crossing some energy barrier and finally reaching some lower energy minimum - just like in thermodynamics (?)

Energy required to cross such energy barrier usually comes from thermal noise - in case of particle decay there would be required some temperature of vacuum ...

 

Generally the universe is built not only of particles, but also can carry different interactions - EM, weak, strong, gravitational. This possibility itself gives vacuum huge amount of degrees of freedom - some fundamental excitations, which not necessarily have nonzero mass like photons ... and if there is some interaction between them, thermodynamics says that they should thermalize - their energy should equilibrate. We can measure thermal noise of EM part of these degrees of freedom - 2.725K microwave background, but degrees of freedom corresponding to the rest of interactions (weak, strong, gravitational) had billions of years to thermalize - should have similar temperature.

The EM part gives about 6*10^-5 of energy of vacuum required to obtain expected cosmological constant, maybe the rest of interactions carries the rest of it ...

 

Anyway we believe that this microwave background is cooling - so 'the temperature of universe' should so.

Shouldn't it became more difficult for particles to cross the energy barrier to get to a lower energy minimum? It would increase decay times ...

We have experimental evidence that physical constants like e,G are unchanged with time, but is it so with decay times?

Maybe radiometric dated things are a bit younger than expected...

Similar situation is for example for excited electrons ...

[SH3RL0CK]

Wouldn't it be great if we could check the decay of particles from past events and compare it to the decay rates observed today? Wait, we can!

 

See: http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

 

From the article:

[edit] Relation to the atomic fine-structure constant

The natural reactor of Oklo has been used to check if the atomic fine-structure constant α might have changed over the past 2 billion years. That is because α influences the rate of various nuclear reactions. For example, 149Sm captures a neutron to become 150Sm, and since the rate of neutron capture depends on the value of α, the ratio of the two samarium isotopes in samples from Oklo can be used to calculate the value of α from 2 billion years ago.

 

Several studies have analysed the relative concentrations of radioactive isotopes left behind at Oklo, and most (but not all) have concluded that nuclear reactions then were much the same as they are today, which implies α was the same too.[7][8]

 

While this case study isn't conclusive, its very convincing to me that the decay rates haven't changed over time.

[Duda Jarek]

I'm not taking about fine-structure constant - it's a combination of some fundamental physical constants.

I'm also not talking about absorption like neutron capture - in these cases the energy barrier is crossed thanks of energy of captured particle.

 

I'm talking about decay - there is a stable state and after some statistical time it spontaneously exceed the energy barrier which made it stable and drops to a lower stable state ... where energy required to cross the barrier comes from?

For me it's clearly thermodynamical process ... this energy has to came form some thermal noise ...

[swansont]

Does decay depend on temperature?

[CharonY]

Well, for electron-capture decay the half time accelerated by a whooping 1.5% by going from 293 to 5 K (provided the measurements are accurate).

 

http://www.ncbi.nlm.nih.gov/pubmed/17678017

 

But this is a special case which has not impact on dating.

[swansont]

Well, for electron-capture decay the half time accelerated by a whooping 1.5% by going from 293 to 5 K (provided the measurements are accurate).

 

http://www.ncbi.nlm.nih.gov/pubmed/17678017

 

But this is a special case which has not impact on dating.

 

Electron capture also depends on pressure, but both of these are known effects due to the mechanism.

[Duda Jarek]

Thanks for the paper.

It's surprising for me that decay is faster in lower temperature ...

 

Generally 2.7K looks to be much too small to have some essential influence on such processes ... I don't like this explanation, but remaining way to cross such energy barrier is some kind of tunneling ...

 

About 'the temperature of vacuum' (2.7K)

- the existence of different interactions (weak, strong, gravitational), which should be carried by some fundamental excitations (modes),

- the requirement of quite large cosmological constant - energy of vacuum,

strongly suggest that there is more than observed EM modes - microwave radiation.

The speed of loosing temperature by black body radiation suggests that it's made practically only by photons - EM modes, so interactions with these 'other modes' should be extremely weak.

The idea of this topic was the only way I could think of to observe directly these 'other modes' ... but they are probably too weak ...

 

The standard 293K temperature known from chemistry is stored in kinetic and EM energy and they interact extremely weakly with these 'other modes' - the rate of thermalisation between them should be extremely slow - they probably could thermalise in billions of years, but for time scale used by us, these temperatures - chemical (~293K) and of 'the other modes' (~2.7K) can be different.

[CharonY]

Electron capture also depends on pressure, but both of these are known effects due to the mechanism.

Yes indeed. I wanted only to point out that temperature (and pressure) do have an effect in special cases. I should have noted that it is not due to increase or decrease of energy, but rather increasing the chance that an electron encounters a nucleus.

[Duda Jarek]

Extremely important news: http://news.stanford.edu/news/2010/august/sun-082310.html

Decay times depend on sun activity!

 

It's another argument that we shouldn't look at nucleuses from blurred, fluctuating quantum picture ( http://www.physorg.com/news199711994.html ), but rather as a concrete spatial structure near (local?) energy minimum (so called soliton).

To get it out of this local minimum, there is needed energy - many orders of magnitude larger than in chemistry.

Standard assumption: Boltzmann distribution suggests that rarely, but it really can spontaneously gather huge amount of energy ... but maybe it's only idealization, chemistry can have some limits ... and so we should search for another source of this energy ... like neutrinos!

 

Consequences? Besides the need to reconsider datings, planetary models ...

Look at hypothetical proton decay - required by particle models like supersymmetry, useful to explain nonzero baryonic number o our universe ... but not observed in huge water tanks - maybe required energy to get proton out of extremal deep potential well is just larger than accessible by chemistry or solar neutrinos?

Safer place to search for it would be extreme temperatures like the core of neutron star - such decay would be Nature's failsafe to prevent infinite matter densities - they would change into energy earlier ... it could also help to explain beyond GZK cosmic rays ...

[swansont]

 

Consequences? Besides the need to reconsider datings, planetary models ...

Look at hypothetical proton decay - required by particle models like supersymmetry, useful to explain nonzero baryonic number o our universe ... but not observed in huge water tanks - maybe required energy to get proton out of extremal deep potential well is just larger than accessible by chemistry or solar neutrinos?

Safer place to search for it would be extreme temperatures like the core of neutron star - such decay would be Nature's failsafe to prevent infinite matter densities - they would change into energy earlier ... it could also help to explain beyond GZK cosmic rays ...

 

No, actually the first consequence is that you do more experiments and get more data to ensure that this is not some sort of statistical fluke. These events were observed in experiments measuring other effects; one really needs to do a series of experiments whose goal is to measure this, specifically. All of this needs to happen before any textbooks are rewritten.

[Duda Jarek]

Experimental evidence started in 80s or earlier http://www.sciencedirect.com/science?_ob=MiamiCaptionURL&_method=retrieve&_udi=B6TJ1-4WDGCNK-1&_image=fig1&_ba=1&_user=4420&_coverDate=08%2F31%2F2009&_alid=1441903185&_rdoc=1&_fmt=full&_orig=search&_cdi=5297&_issn=09276505&_pii=S092765050900084X&view=c&_acct=C000059607&_version=1&_urlVersion=0&_userid=4420&md5=3d9cea58f6a7c0f05dcf360a29dabe08 and there is much more of them, for different isotopes and with huge statistical analysis ... in many papers accepted by reviewers of good journals...

Do you know peer-reviewed papers claiming opposite results?

 

What are they showing...

That mathematical idealization - decay time of nucleus is constant only approximately ...

Why can we be sure that these coefficient from Poisson theorem (extremely many of extremely rare chances) are really constant?

Shouldn't we really understand nuclear/particle physics before such claims? Do we?

 

Here is more discussion: http://www.symmetrymagazine.org/breaking/2010/08/23/the-strange-case-of-solar-flares-and-radioactive-elements/

Edited August 27, 2010 by Duda Jarek

[swansont]

If these are reactions that are caused by interactions with solar neutrinos, then they are, by definition, not decays, and what we are observing would be the combination of two effects: spontaneous decay, and an induced reaction. We already know induced reactions of this sort exist; they are how neutrino detectors work. The big question would be in regard to the size of the cross-section. So until a more precise determination is made as to what combination of effects are present, the conclusions about changing decay rates are premature. That's why you need to do a series of experiments dedicated to this; merely noting a fluctuation only tells you that there is something further to study. It doesn't answer the question of what is actually going on.

 

Peer-reviewed papers claiming the opposite? I don't think there would be any which specifically looked at the effects to rule it out; you generally don't report null results for things you weren't testing. (For example, I have not seen any effects of local cicada population on any of the clock outputs for the devices I'm building, and I'm not going to mention that in a paper. Why would I?) Reporting this phenomenon represents a deviation from previous experiment, so how about all of the ones determining the decay rates in the first place? And the ones refining those numbers? They did not report any noticeable fluctuations. Maybe they'll go back and look at their past data, if they can, just to be sure.