Convergence or Disruption?
Particle View
Joe Lykken
Fermilab
8 October 2019

The Early-Late Hubble constant tension:
Convergence or Disruption?
My prediction:

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J. Lykken | Cosmic Controversies

The Early-Late Hubble constant tension:
Convergence or Disruption?
My prediction:

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J. Lykken | Cosmic Controversies

The Early-Late Hubble constant tension:
Convergence or Disruption?
My prediction: Convergence• It is a triumph of precision astronomy to see the kind of mature data analysispresented [and argued about] at this conference• As Roger Blandford said, tensions are normal• In the world of particle physics we have learned to be very patient about suchtensions – they can take a decade or more to resolve• Based on historical precedent [not any expertise], I would agree with Roger thatthe current tension is more likely to be caused by some combination ofsystematics, measurement issues, and astrophysics issues, rather than new
fundamental ingredients

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Caveats on the 5 sigma “gold standard’• In particle physics a 5 sigma deviation is considered a necessary but not
sufficient condition, to claim a discovery• One reason is that in the real world there is no such thing as a 5-sigma
Gaussian deviation, because in the real world distributions have nonGaussian flat tails• Thus even after you work really hard to estimate your total 1 sigma
uncertainty, the probability of an excursion 5 times this value is usuallymuch higher than the p-value for Gaussian 5 sigma• Thus for example in the CMS experiment we fit nominally Gaussian
distributions with a “Cruijff function”, that has flat tails built in• Furthermore some 5 sigma discrepancies are resolved by (eventual)community consensus to discount a particular experiment or set ofmeasurements, even though the flaw in those measurements is neverclearly identified. [e.g. DAMA]

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J. Lykken | Cosmic Controversies

Explanation of Cosmic Acceleration:
Convergence or Disruption?
My prediction:

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J. Lykken | Cosmic Controversies

Explanation of Cosmic Acceleration:
Convergence or Disruption?
My prediction:

noitpursi
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J. Lykken | Cosmic Controversies

Explanation of Cosmic Acceleration:
Convergence or Disruption?
My prediction: Disruption• I am surprised at the varying reactions to what Joe Silk called “the worst prediction in physics”,
i.e. the 120 order of magnitude discrepancy in the vacuum energy as measured by cosmic
expansion• To me this embarrassment shows one thing: that we don’t know how to do the calculation• This is not too surprising since the LHC seems to be telling us that we don’t know how to do thesimilar calculation for the Higgs mass and the electroweak scale in naïve extensions of theStandard Model• The latter is related to issues of naturalness in extensions of the Standard Model• Note that the Standard Model itself does not have a naturalness problem, since the Higgs massand the electroweak scale are not predicted: they are empirical parameters• Note however that in the SM the QCD scale ~ 300 MeV is predicted [in terms of log running ofa dimensionless parameter], and this scale is intermediate between the electroweak scale andthe scale of dark energy
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J. Lykken | Cosmic Controversies

NATURAL SUSY, 1984

Explanation of Cosmic Acceleration:
Convergence or Disruption?
My prediction: Disruption• We have been using naturalness arguments tomotivate experimental searches for at least 35 years
now, with zero success• My personal belief is that these arguments arefundamentally wrong when applied to extensions ofthe SM, and that eventually some smart young
person will articulate why, creating a disruption• In any event it is clear that this approach is notworking very well, so it is time to strongly encouragealternative approaches• For example I was happy to see Justin Khoury
suggesting that the near-criticality of the Higgs
should be a focus of our attention
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J. Lykken | Cosmic Controversies

SUSYSpectrum,
1984
From LawrenceHall’stalk at SavasFest
W boson near
the top of thespectrum....
1984 was autopian year
for SUSY.
Times havechanged!

Text
Over 3 decades of susy: seismic shifts!

slide stolen from Matt Reece

NATURAL SUSY, 1984

Explanation of Cosmic Acceleration:
Convergence or Disruption?
My prediction: Disruption

SUSYSpectrum,
1984
From LawrenceHall’stalk at SavasFest
W boson near
the top of thespectrum....
1984 was autopian yearfor SUSY.

• We have been using naturalness arguments tomotivate experimental searches for at least 35 years
now, with zero success
Text
Times have
• My personal belief is that these arguments arefundamentally wrong when applied to extensions of changed!
Over 3 decades of susy: seismic shifts!
the SM, and that eventually some smart young
slide stolen from Matt Reeceperson will articulate why, creating a disruption• In any event it is clear that this approach is notworking very well, so it is time to strongly encouragealternative approaches
I therefore propose a voluntary 10-year• For example I was happy to see Justin Khoury
moratorium on the use of the word
suggesting that the near-criticality of the Higgs
should be a focus of our attention“naturalness” in scientific publications
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J. Lykken | Cosmic Controversies

Multiverse or not:Convergence or Disruption?
My prediction:

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J. Lykken | Cosmic Controversies

Multiverse or not:Convergence or Disruption?
My prediction:

noitpursi
D
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J. Lykken | Cosmic Controversies

The peek-a-boo universe?
Is the hypothesis of eternal inflation as a generic mechanism creating a multiverse a“plausible scientific theory”? [Alan Guth]My answer:• Yes it is both plausible and scientific [and possibly wrong]• By “plausible” I mean that there is already substantial observation evidence forprimordial inflation, and that at least in the “cartoon” version of inflation it appears
that eternal inflation is generic• By “scientific” I mean that one can imagine over time gathering additional evidence
that will either support [but not prove] or disfavor [but not disprove]• Just because the rest of the putative multiverse is not observable today doesn’tmean that we cannot at some confidence level assert that it is there• This is not so different from the first scientific discovery that every infant makes atage 18 months: the discovery of object permanence• Also I agree with Alan that once we develop a robust theory of universe formation
we might reasonably conclude that it would be very odd if ours is the only
instantiation

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Anthropic Angst“I would advocate anthropic explanations be thought of as explanations of last resort” [Alan Guth]I strongly agree with this:• It is pretty obvious that certain features of our existence are explained at least in part by anthropic
reasoning• So applied sparingly and with rigor, anthropic reasoning can be scientific [but beware falling into thekinds of traps that social Darwinists and evolutionary psychologists get caught in]• My real concern is that we may be jumping to the “last resort” prematurely• Just because we seniors were too stupid to figure a better explanation for the cc, doesn’t mean thatthe younger generation will not make a breakthrough• It is our responsibility as seniors to support the possibility of radically new approaches rather than
discounting it

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J. Lykken | Cosmic Controversies

Anthropic Angst“I would advocate anthropic explanations be thought of as explanations of last resort” [Alan Guth]I strongly agree with this:• It is pretty obvious that certain features of our existence are explained at least in part by anthropic
reasoning• So applied sparingly and with rigor, anthropic reasoning can be scientific [but beware falling into thekinds of traps that social Darwinists and evolutionary psychologists get caught in]• My real concern is that we may be jumping to the “last resort” prematurely• Just because we seniors were too stupid to figure a better explanation for the cc, doesn’t mean thatthe younger generation will not make a breakthrough• It is our responsibility as seniors to support the possibility of radically new approaches rather than
discounting it
I therefore propose a voluntary 10-year moratorium on the use of the word “anthropic” in scientificpublications

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Don’t drain the swamp
In my view the scientific hypothesis of a multiverse is only very weakly connected to the string theory
landscape or the swampland of non-string-compatible EFTs
• The argument that the only possible UV completions of the Standard Model with gravity are in string
theory was mostly along the lines of “nobody has come up with any other examples”• Instead I regard string theory more as a useful theoretical laboratory for talking about and learning
about quantum gravity (especially AdS/CFT), rather than as The Theory of Our Universe• It is certainly interesting to try to understand the Landscape and the Swampland• But from the view of cosmology I would assert that it is much more interesting and potentially usefulto use string theory to investigate cosmological singularities like the Big Bang
• However papers on the former seem to outnumber papers on the latter by log(10^500) to 1

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J. Lykken | Cosmic Controversies

Dark matter beyond WIMPs:
Convergence or Disruption?
My prediction:

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J. Lykken | Cosmic Controversies

Dark matter beyond WIMPs:
Convergence or Disruption?
My prediction:

noitpursi
D
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J. Lykken | Cosmic Controversies

Dark matter beyond WIMPs:
Convergence or Disruption?
My prediction: Disruption• Let’s be honest that the main motivation for ~100 GeV WIMPs was supersymmetry, not
the WIMP Miracle• This is not to discount the importance of the incredibly powerful direct searches currently
planned or underway• But we had better have a broader direct detection program that covers a larger fraction of
the possible mass range• And we had better think about what we are going to do if DM particles have only
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J. Lykken | Cosmic Controversies

Dark matter beyond WIMPs:
Convergence or Disruption?
The good news:• There is overwhelming evidence that dark matter exists and consists of one or more kinds ofparticles [or clumps thereof]• I support the approach advocated by Kathryn Zurek with addendum from Elena Aprile:• Pick a target with some theory motivation and benchmarks• Figure out how to probe it and what you need to build to do that
• Start small and iterate, learning about the backgrounds as you go• It is our good luck that many relevant new detection technologies are appearing just as we haverealized that we need them
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Dark matter beyond WIMPs:Convergence or Disruption?
The good news: National Quantum Initiative

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J. Lykken | Cosmic Controversies

Fermilab collaborations on quantum sensors• Fermilab is collaborating with 22 universities and other labs on quantum R&D, witha large fraction related to quantum sensors• The very challenging science goals like laboratory detection of dark matter, are now
driving advances in quantum technologies; these advances will eventually havebroad impact beyond particle physics

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J. Lykken | Cosmic Controversies

Fermilab Dark SRF Experiment: produce and detect dark photons

Tunable powered “Emitter”
SRF cavity and quiet“Receiver” SRF cavity, tuned towithin 1 Hz
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Prototype “R2D2” ready fortesting: supported by the DOE
QuantISED program

J. Lykken | Cosmic Controversies“Run 1” in the Fermilab Vertical Test
Stand used for cryogenic tests of SRF
cavities; “Run 2” in dilution fridge

Physics Today, June 2019
• axion dark matter searches are already limited byquantum noise• new quantum sensing techniques are needed tomake further progress towards higher mass axions.

https://physicstoday.scitation.org/doi/10.1063/PT.3.4227

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MAGIS-100 cold atom gradiometer:

an incredibly sensitive quantum measuring device, first of its kind
• 100 meter vacuum system with 3 atom interferometers driven by a single
laser system• Use the same ultra-cold strontium atoms that are the basis of the best
atomic clocks• Proof-of-concept used the Stanford prototype• Advancing quantum science with long-range superposition, coherence andentanglement of atoms• Sensitivity to ultralight dark matter• Technology pathfinder for future midband gravitational wave detectors

Jason Hogan PI(Stanford)

supported by the DOE QuantISED program
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Two assembled Sr atom sources

MINOS shaft atFermilab

Final words of wisdom:• Saul Perlmutter: “Cosmology is still a pretty young field,
so I still expect major new developments on relatively
short timescales”• Justin Khoury: “A drunken man will find his way home,
but a drunken bird is lost forever”• Roger Blandford: “Discoveries are like burglars – theybreak in through the side window instead of walking in
the front door”
Jim Peebles: What might we learn from lines of research thatare off the beaten track? They check accepted ideas, always aGood Thing, and there is the chance Nature has prepared yet
another surprise for us.
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