and now for something completely different……

And Now For And Now For Something Something Completely Completely

Different……Different……

31 August 201131 August 2011 John Learned at Harvard Club, HonoluluJohn Learned at Harvard Club, Honolulu 11

John LearnedJohn LearnedUniversity of HawaiiUniversity of Hawaii

Galactic Neutrino Galactic Neutrino Communication & SETICommunication & SETI

31 August 201131 August 2011 John Learned at Harvard Club, HonoluluJohn Learned at Harvard Club, Honolulu 22

(SETI=Search for Extra-Terrestrial Intelligence)

“Work” in collaboration with Sandip Pakvasa (UH), Walt Simmons (UH), Xerxes Tata (UH), Tony Zee (UCSB), Rolf-Peter Kudritzki (UH)

This work is NOT supported by: DOE, NSF, NASA, DOD, DARPA…….….. Not even by the SETI Institute! But much beer was needed in production.

Long Distance Neutrino Long Distance Neutrino Communication is an old idea:Communication is an old idea:

H. Saenz et al., 1977H. Saenz et al., 1977 J. Albers, P. Kotzer & D.Padgett, 1978J. Albers, P. Kotzer & D.Padgett, 1978 M. Subotowicz, 1979M. Subotowicz, 1979 J. Pasachoff & M. Kutner, 1979J. Pasachoff & M. Kutner, 1979

They had the basic idea to use neutrino beams forThey had the basic idea to use neutrino beams forinterstellar and terrestrial communication based interstellar and terrestrial communication based on the penetrating power of neutrinos……….on the penetrating power of neutrinos……….

Also proposed use for communicating with submarines, Also proposed use for communicating with submarines, getting getting

the US Navy interested! (Needless to say, one way only!)the US Navy interested! (Needless to say, one way only!)

A recent proposal is to use neutrino beams from muonA recent proposal is to use neutrino beams from muoncolliders: Z. Silagadze, arXiv:0803.0409(2008). colliders: Z. Silagadze, arXiv:0803.0409(2008). Idea of neutrino communication with submarines has been Idea of neutrino communication with submarines has been revived very recently: P. Huber, arXiv:0909.4554(2009).revived very recently: P. Huber, arXiv:0909.4554(2009).

31 August 201131 August 2011John Learned at Harvard Club, John Learned at Harvard Club,

HonoluluHonolulu 33

SETI: SETI: Search for Extra-Terrestrial IntelligenceSearch for Extra-Terrestrial Intelligence There should/might be many advanced There should/might be many advanced

civilizations(ETI) out there in the galaxy……civilizations(ETI) out there in the galaxy……

Fermi’s question(1950): “So, where are they?” Fermi’s question(1950): “So, where are they?” Namely, if they are out there why haven't we seen Namely, if they are out there why haven't we seen or heard from them? Why are they not here?or heard from them? Why are they not here?

Maybe security concerns prevent them from Maybe security concerns prevent them from revealing themselves?revealing themselves?

Maybe they would like to send info on a variety of Maybe they would like to send info on a variety of topics…..?topics…..?

Too Many Possible Scenarios, no point in trying to Too Many Possible Scenarios, no point in trying to guess, just look for signals…guess, just look for signals…


HonoluluHonolulu 44

History/origin of History/origin of “The Fermi Question”“The Fermi Question”

1950: Herb York, Edward Teller, Emil 1950: Herb York, Edward Teller, Emil Konopinski and Enrico Fermi were meeting for Konopinski and Enrico Fermi were meeting for lunch at the Los Alamos Laboratory. Before lunch at the Los Alamos Laboratory. Before Fermi arrived, the talk was abut a recent Fermi arrived, the talk was abut a recent cartoon in the New Yorker magazine about cartoon in the New Yorker magazine about two recent headline making news-reports, two recent headline making news-reports, – one on flying saucers and one on flying saucers and – the other on disappearing trash cans in NYC! the other on disappearing trash cans in NYC!


HonoluluHonolulu 55

On arrival, Fermi’s reaction was that On arrival, Fermi’s reaction was that the the “model” in the cartoon was the the “model” in the cartoon was obviously correct as it explained TWO obviously correct as it explained TWO unrelated events!unrelated events!

Later during the lunch, in the middle Later during the lunch, in the middle of a conversation about something of a conversation about something else altogether, Fermi is reported to else altogether, Fermi is reported to have exclaimed “So, where are have exclaimed “So, where are they?”they?”

It was clear to the others what he It was clear to the others what he had meant……..had meant……..


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Fermi’s Question has given rise to much Fermi’s Question has given rise to much discussion and attempts to answer it… discussion and attempts to answer it…

including books..including books.. One implication was that One implication was that

since we have not since we have not seen/heard from them, seen/heard from them, there are no ETI: there are no ETI: there is there is no one out there. no one out there.

One simple response is: One simple response is: Absence of evidence is Absence of evidence is NOT evidence of absenceNOT evidence of absence!!

An even simpler and An even simpler and telling one is due to Calvin telling one is due to Calvin and Hobbes: The fact that and Hobbes: The fact that no one has tried to no one has tried to contact us IS Itself Proof of contact us IS Itself Proof of Extra terrestrial Extra terrestrial Intelligence!! (November Intelligence!! (November 12, 2008).12, 2008).


HonoluluHonolulu 77

Comment in Comment in the Walt Kelly the Walt Kelly

Strip “Pogo Strip “Pogo Possum” by Possum” by Porky Pine:Porky Pine:

““There’s only two possibilities. There is There’s only two possibilities. There is life out there in the Universe that’s life out there in the Universe that’s smarter than we are, or we’re the most smarter than we are, or we’re the most intelligent life in the Universe. Either intelligent life in the Universe. Either way, it’s a mighty sobering thought.”way, it’s a mighty sobering thought.”


HonoluluHonolulu 88


HonoluluHonolulu 99

http://arxiv.org/ftp/arxiv/papers/1104/1104.4462.pdf


HonoluluHonolulu 1010

These authors consider a number of scenarios ranging from optimistic to most pessimistic.

Interesting ImplicationsInteresting Implications

Many have warned about danger from Many have warned about danger from contact (Carl Sagan, Jared Diamond, contact (Carl Sagan, Jared Diamond, Martin Royle, Stephen Hawking…)… Martin Royle, Stephen Hawking…)… think of the history of humans!think of the history of humans!

However, an exponentially expansive However, an exponentially expansive species (think movie “Alien”) probably species (think movie “Alien”) probably does not exist or they would be here does not exist or they would be here now! Unless they collapsed….now! Unless they collapsed….





For decades (~ 50 years) Standard For decades (~ 50 years) Standard Searches for ETI have concentrated on Searches for ETI have concentrated on radio (e.g. the 21 cm line), microwave radio (e.g. the 21 cm line), microwave or optical frequencies (all are photons)or optical frequencies (all are photons)

Photons can be obscured/attenuated as Photons can be obscured/attenuated as opposed to neutrinos; also scattered opposed to neutrinos; also scattered leading to jitter in time & direction.leading to jitter in time & direction.

Less backgrounds and noise for a Less backgrounds and noise for a Neutrino signal, so….Neutrino signal, so….

Neutrinos & SETI: Obviously a very Neutrinos & SETI: Obviously a very hot topic judging by citations:hot topic judging by citations:

Walt Simmons, John Learned, Xerxes Tata, Sandip Pakvasa, Walt Simmons, John Learned, Xerxes Tata, Sandip Pakvasa, Q. J. Roy. Q. J. Roy. Astro. Soc. (1994).Astro. Soc. (1994).

#Citations= #Citations= 11

John Learned, Tony Zee, Sandip Pakvasa, John Learned, Tony Zee, Sandip Pakvasa, Phys. Lett. B(2009).Phys. Lett. B(2009).

#Citations = #Citations = 33

John Learned, Tony Zee, Rolf-Peter Kudritzki, Sandip Pakvasa, John Learned, Tony Zee, Rolf-Peter Kudritzki, Sandip Pakvasa, arXiv:0809.0339(rejected by Phys. Rev. Lett., in press Contemporary arXiv:0809.0339(rejected by Phys. Rev. Lett., in press Contemporary Physics).Physics).

#Citations = #Citations = 00

Although many in non-technical magazine e.g. The Economist etc……!Although many in non-technical magazine e.g. The Economist etc……!



Good thing we have tenure.

““Talking to the neighbors”Talking to the neighbors”

11 May 201111 May 2011 John Learned at KITPJohn Learned at KITP 1414

“A modest proposal for an interstellar communications network”Economist, 7 April 2011

http://www.economist.com/PrinterFriendly.cfm?story_id=18526871

SETI with Neutrinos

Three Possible Nu ScenariosThree Possible Nu Scenariosto discussto discuss

Timing-Data Communication with Timing-Data Communication with neutrinosneutrinos

Sending a focused beam of neutrinos ofSending a focused beam of neutrinos of a definite energya definite energy

Disturbing a Cepheid variable star with Disturbing a Cepheid variable star with a neutrino beam to modulate its perioda neutrino beam to modulate its period

Will only cover the latter today…Will only cover the latter today…



Cepheids variables and Cepheids variables and the cosmic distance the cosmic distance

ladderladder

Henrietta Leavitt’s (Harvard Henrietta Leavitt’s (Harvard Observatory) discovery of the Observatory) discovery of the luminosity-period relation luminosity-period relation allowed Hubble to make his allowed Hubble to make his discovery & made cosmology discovery & made cosmology possible (see recent biography possible (see recent biography “Miss Leavitt’s Stars”)“Miss Leavitt’s Stars”)

Learned, Kudritzki, Pakvasa, & Zee

http://xxx.lanl.gov/PS_cache/arxiv/pdf/0809/0809.0339v2.pdf, in press Contemporary Physics

1908:



http://xxx.lanl.gov/PS_cache/arxiv/pdf/0809/0809.0339v2.pdf

http://xxx.lanl.gov/PS_cache/arxiv/pdf/0809/0809.0339v2.pdf

• A Cepheid variable is a member of a particular class of variable stars, notable for tight correlation between their period of variability and absolute luminosity.

• Namesake and prototype of these variables is the star Delta Cephei, discovered to be variable by John Goodricke in 1784.

• This correlation was discovered and stated by Henrietta Swan Leavitt in 1908 and given precise mathematical form by her in 1912.

• Period-luminosity relation can be calibrated with great precision using the nearest Cepheid stars.

• Distances found with this method are among the most accurate available.

- Leavitt, Henrietta S. "1777 Variables in the Magellanic Clouds". of Harvard College Observatory. LX(IV) (1908) 87-110.

- P C. "Periods of 25 Variable Stars in the SMC". Harvard College Circular 173 (1912) 1-3.



The Cepheid variables proved The Cepheid variables proved very very useful:very very useful:

In 1915 they were used by Harlow In 1915 they were used by Harlow Shapley to measure the size & Shapley to measure the size & shape of the milky way, and the shape of the milky way, and the location of the sun in it.location of the sun in it.

In 1924, Edwin Hubble used them to In 1924, Edwin Hubble used them to measure distance to the measure distance to the Andromeda galaxy and proved that Andromeda galaxy and proved that it is not part of the milky way! (End it is not part of the milky way! (End of the Island Universe idea!)of the Island Universe idea!)

In 1929, Humason and Hubble In 1929, Humason and Hubble

showed that the universe is showed that the universe is expanding!expanding!

In mid –’40s, Baade showed that In mid –’40s, Baade showed that

there are two different classes of there are two different classes of Cepheid variables with differing Cepheid variables with differing velocity-luminosity relationship velocity-luminosity relationship and thus revised and thus revised

the distance scale by about a factor the distance scale by about a factor of 2……(classical and type II).of 2……(classical and type II).



Measure period and apparent magnitude (brightness),

Period -> Absolute magnitude

Distance = RefDist x sqrt(Absolute/Apparent)

Cepheid MechanismCepheid Mechanism



Cepheid usually a population I giant yellow star, pulsing regularly by expanding and contracting, regular oscillation of its luminosity from 103 to 104 times L☼

Cepheids, population I stars: “Type I Cepheids”, Similar (population II) W Virginis: Type II Cepheids.

Luminosity variation due to cycle of ionization of helium in the star's atmosphere, followed by expansion and deionization. Key: ionized, the atmosphere more opaque to light.

Period equal to the star's dynamical time scale: gives information on the mean density and luminosity.

Model for Cepheid VariablityModel for Cepheid Variablity

Basic idea given by Eddington in 1917:Basic idea given by Eddington in 1917:

Doubly ionized He is more opaque(than, Doubly ionized He is more opaque(than, say singly ionized He) At the dimmest say singly ionized He) At the dimmest point of the cycle, the gas is most point of the cycle, the gas is most opaque, and outermost layers heat and opaque, and outermost layers heat and expand, as the gas expands, it begins to expand, as the gas expands, it begins to cool, so becomes less ionized and hence cool, so becomes less ionized and hence more transparent, radiation escapes. more transparent, radiation escapes. The expansion stops and star contracts The expansion stops and star contracts due to gravity. And the process repeats.due to gravity. And the process repeats.

(The identification of He was due to Zhevakin (The identification of He was due to Zhevakin

in 1953 . Extensive detailed modeling for the P in 1953 . Extensive detailed modeling for the P and time variation of P exists in the and time variation of P exists in the literature.) literature.)



Cepheid Light CurvesCepheid Light Curves



Typical saw tooth pattern

Sample of data fromHubble Key project measured 800 Cepheids, out through Virgo Cluster

Period-luminosity relation

Feast & Catchpole, 1997

Interlude: Interlude: What’s a What’s a Neutrino?Neutrino?



11 May 201111 May 2011 John Learned at KITPJohn Learned at KITP 2323Thanks Joshua Murillo

Neutrino Contents about 0.0000000000000000002 kCal

Breakfast Nus?


uuupup

dddowndown

cccharmcharm

tttoptop

ssstrangestrange

bbbottombottom

eeelectronelectron

ννeeelectronelectronneutrinoneutrino

μμmuonmuon

ττtauontauon

ννμμmuonmuonneutrinoneutrino

ννττtautauneutrinoneutrino

Quark

sQ

uark

sLe

pto

ns

Lepto

ns

unstableunstable

νν??sterilesterileneutrinoneutrino

νν??sterilesterileneutrinoneutrino

glu

on

photo

n

W &

Z


Where do Neutrinos come Where do Neutrinos come from?from?

Astrophysical SourcesAstrophysical Sources

Soon ?Soon ?

Astrophysical SourcesAstrophysical Sources

Soon ?Soon ?

Nuclear ReactorsNuclear Reactors(power stations, ships)(power stations, ships)

Nuclear ReactorsNuclear Reactors(power stations, ships)(power stations, ships)

Earth’s AtmosphereEarth’s Atmosphere(Cosmic Rays)(Cosmic Rays)

Earth’s AtmosphereEarth’s Atmosphere(Cosmic Rays)(Cosmic Rays)

SunSunSunSun

SupernovaeSupernovae(star collapse)(star collapse) SN 1987ASN 1987A

SupernovaeSupernovae(star collapse)(star collapse) SN 1987ASN 1987A

Big BangBig Bang(here 330 (here 330 /cm/cm33)) Indirect EvidenceIndirect Evidence

Big BangBig Bang(here 330 (here 330 /cm/cm33)) Indirect EvidenceIndirect Evidence

Bulk EarthBulk Earth(U/Th Radioactivity)(U/Th Radioactivity)

Bulk EarthBulk Earth(U/Th Radioactivity)(U/Th Radioactivity)

Particle AcceleratorParticle AcceleratorParticle AcceleratorParticle Accelerator

What do we know well What do we know well about neutrinos?about neutrinos?


• No electric charge.• Little or no electric/magnetic dipole moment.• Essentially point particles.• Very small mass compared to other fermions.• Participates only in SM weak interaction.• Falls under gravity (SN1987A).• Produced in only left-handed helicity state (nubar = righthanded)• Comes in three flavors, e, μ and τ• Lepton number is conserved (but not lepton flavor)• No known lifetime (but…).• Has nothing to decay to amongst known particle zoo (but νm-> νn OK)• SM processes produce neutrinos as superposition of mass states• Mass states’ relative phases change with flight time, producing morphing between interaction states (“ν oscillations”).• Three mass states explains all accepted data, but room for new things.• Almost surely we are living in a bath of undetectable ~600nu/cm3

left from Big Bang, which travel ~300 km/s.

Back to Nu SETIBack to Nu SETI



Main thing for present purposes:

We understand neutrinos rather well.

We know how to make beams of neutrinos.

They can penetrate even deep into stars.

When they do stop, they can deliver a lot of energy.

How to modulate the How to modulate the period and create a period and create a

signal ?signal ?

If the period can be modulated one If the period can be modulated one can observe this signal over can observe this signal over enormous distances --- intergalactic!enormous distances --- intergalactic!

This requires depositing energy deep This requires depositing energy deep inside the star so that the cycle ends inside the star so that the cycle ends earlier and the period is shortened….earlier and the period is shortened….

This is where neutrinos come in, as This is where neutrinos come in, as any other method will not reach deep any other method will not reach deep inside the star…..inside the star…..



Neutrino Beam to Tickle a Neutrino Beam to Tickle a Star?Star?

Idea is to use neutrinos to deliver Idea is to use neutrinos to deliver energy at controlled depth to star, as energy at controlled depth to star, as giant amplifier.giant amplifier.

Cepheids fill this need…. Bright Cepheids fill this need…. Bright pulsing stars with period of pulsing stars with period of instability.instability.

Any civilization would monitor Any civilization would monitor Cepheids as distance markers.Cepheids as distance markers.

Can be seen from distant galaxies Can be seen from distant galaxies (we see Cepheids in the Virgo (we see Cepheids in the Virgo cluster).cluster).



.. Try to avoid details (which we cannot Try to avoid details (which we cannot

know) here, consider big picture.know) here, consider big picture.

Guess at energy input: take Guess at energy input: take deposition time of roughly speed of deposition time of roughly speed of sound crossing nucleus (~0.1 s). sound crossing nucleus (~0.1 s).

Take power to be 10% of stellar core Take power to be 10% of stellar core output. output.

Need Pwr ~10Need Pwr ~10-6-6 L Lcephceph . Few day . Few day Cepheid, would need 10Cepheid, would need 102828 J! But, J! But, NOT OUR PROBLEM! NOT OUR PROBLEM!



Tickling a Cepheid….?Tickling a Cepheid….?

Could be much less needed… have not done studies. Not Could be much less needed… have not done studies. Not useful for now.useful for now.

Not to melt, need accelerator at r>100 AU, capture Not to melt, need accelerator at r>100 AU, capture radiation from area ~0.1AUradiation from area ~0.1AU22

Accelerators are efficient, well known physics at lower Accelerators are efficient, well known physics at lower powers, but need large technology extrapolation.powers, but need large technology extrapolation.

Want neutrinos of order 1 TeV to deposit energy deep inside Want neutrinos of order 1 TeV to deposit energy deep inside star with exponentially increasing density (energy choice star with exponentially increasing density (energy choice selects radius of deposition).selects radius of deposition).

Studies needed to determine how little one needs to jump Studies needed to determine how little one needs to jump start expansion. But we need not solve that problem for start expansion. But we need not solve that problem for present purposes, simply aver that it is solvable and the ETI present purposes, simply aver that it is solvable and the ETI would do so.would do so.



Light Curve of Simulated Light Curve of Simulated CepheidCepheid



• Ordinate is stellar magnitude relative to the mean, abscissa is time in days.

• Solid curve: unmodulated (idealized) Cepheid with 2 day period and 2 magnitude luminosity excursion, with expansion taking 0.4 days.

• Dashed curve: arbitrarily modulated light curve with triggered phase advance of 0.1 day (0.05 cycle) (Data = 1110000010100110).

• Units arbitrary but representative of real data.

•The sharpness of the transitions does not matter for the present discussions.

Fourier TransformsFourier Transforms



Abscissa is frequency, 1/days.

Ordinate is the Lomb-Scargle parameter, similar to chi squared;

• Fourier spectra of simulated observations of a regular periodic Cepheid variable andone with binary phase modulation. • More complicated structure of the modulated case is not so obviously different from a noisy spectrum: one could not immediately discern that the latter case was not ``natural’’.

Frequency 1/days

Frequency 1/days

Unmodulated

Modulated

normal

modulated

Cepheid spectra

How to recognize an How to recognize an ETI Signal?ETI Signal?

Information theory says maximally compact Information theory says maximally compact data is indistinguishable from noise.data is indistinguishable from noise.

Interesting question: how can one tell for sure when Interesting question: how can one tell for sure when a signal is not `random’? Or can we tell a ETI signal a signal is not `random’? Or can we tell a ETI signal from a hole in the ground? (to quote John Ellis)from a hole in the ground? (to quote John Ellis)

ETI signal should have inexplicable regularities: ETI signal should have inexplicable regularities: repeated sequences, letters, frames, apparent repeated sequences, letters, frames, apparent structures…. (Applies to all SETI).structures…. (Applies to all SETI).

Who knows how they might encode?Who knows how they might encode?

Hopefully Hopefully we will know it when we see itwe will know it when we see it!!



OutlookOutlook Unstable stellar systems such as the Cepheids Unstable stellar systems such as the Cepheids can serve as gigantic signal amplifiers visible across the universe.can serve as gigantic signal amplifiers visible across the universe.

Assume a sufficiently advanced civilization Assume a sufficiently advanced civilization – able to tickle stars (?)able to tickle stars (?)– find it worthwhile (???). find it worthwhile (???).

Signatures of ETI communication Signatures of ETI communication may be available in data already may be available in data already recordedrecorded,,

and that a search of Cepheid (and perhaps other variable star, such asand that a search of Cepheid (and perhaps other variable star, such as Lyrae) records may reveal an entre’ into the galactic ‘telegraph’!Lyrae) records may reveal an entre’ into the galactic ‘telegraph’!

Certainly a long shot, but should it be correct, the payoff would beCertainly a long shot, but should it be correct, the payoff would be immeasurable for humanity.immeasurable for humanity.

Many possibilities for ETI communication: try all practical ones. Many possibilities for ETI communication: try all practical ones.

The beauty of this suggestion: data already exists, and we need only The beauty of this suggestion: data already exists, and we need only look at it in a new way.look at it in a new way.



ClarificationClarificationWe are NOT proposing to attempt buildingWe are NOT proposing to attempt building

the neutrino beams nor try to tickle thethe neutrino beams nor try to tickle the

nearest cepheid variable star*.nearest cepheid variable star*.

Our proposals are much more modest:Our proposals are much more modest:

Assuming that there may be some ETIAssuming that there may be some ETI

much more advanced technologically than us,much more advanced technologically than us,

and that they may be sending such signalsand that they may be sending such signals

(for whatever reasons of their own), we(for whatever reasons of their own), we

merely propose that we should:merely propose that we should:



*Nearest Cepheid is Polestar at 143 parsecs.

Summary: Action ItemsSummary: Action Items

Look for 45.5 GeV neutrino signal in KM3Look for 45.5 GeV neutrino signal in KM3 Look for 6.3 PeV anti-electron-neutrinos inLook for 6.3 PeV anti-electron-neutrinos in KM3 via Glashow ResonanceKM3 via Glashow Resonance

Analyze Cepheid Data to look for modulation:Analyze Cepheid Data to look for modulation: Signals are spectacular and the searchesSignals are spectacular and the searches are practically free……are practically free……

Large scale neutrino detectors……..”buildLarge scale neutrino detectors……..”build them and they will come” ! them and they will come” !



Not

dis

cuss

ed h

ere

.

Timing Data Communications Timing Data Communications & SETI (1994)& SETI (1994)

Currently our time standards based on Cs Currently our time standards based on Cs Fountain Clocks, accuracy 1 part in 10Fountain Clocks, accuracy 1 part in 101616, , Josephson junctions can potentially go to Josephson junctions can potentially go to 10101919..

Due to chaos and GR corrections, need Due to chaos and GR corrections, need synchronization signals to keep accurate synchronization signals to keep accurate time, not necessarily frequent, e.g. VLBI time, not necessarily frequent, e.g. VLBI will need accurate timing data over huge will need accurate timing data over huge distances. Local clocks need to exchange distances. Local clocks need to exchange timing data to remain synchronized.timing data to remain synchronized.



Hence need stable clocks of highest Hence need stable clocks of highest precision->fast processes for transmitting precision->fast processes for transmitting

and receiving markers & form of radiation and receiving markers & form of radiation to convey faithfully data over enormous to convey faithfully data over enormous distances.distances.

A very advanced ETI would presumably A very advanced ETI would presumably need ever more accurate timing need ever more accurate timing eventually physics limit timing.eventually physics limit timing.

Shortest time interval known today is the Shortest time interval known today is the Z lifetime about 10Z lifetime about 10-25-25 sec. sec.



This suggests use of neutrinos from the decay of Z as an ideal carrier. (open problem: how to make Z-clocks!) We imagine that an ETI is doing just that at distancesof order of kiloparsecs in the galaxy for its own spreadout outposts…We expect to see neutrinos of energy of about 45.5 GeV.To get a few events per year in a KM3 detector, weestimate power requirement at the source to be enormous: about solar luminosity!Such an ETI source would look like a “Dyson shell”!Who knows, after all there are over 50,000 IR sourcesIdentified by IRAS……..In any case this is not OUR problem. (this will be my Mantra). All we need to do is wait and look for the neutrino signal at half the Z mass, clean with no backgrounds. ICECUBE is waiting….Simmons,Learned,Pakvasa & Tata, Q.J.R.Astr.Soc. 35,321(1994)



““Dyson Shell”Dyson Shell” Dyson shell is a name for stars which areDyson shell is a name for stars which arebeing harnessed by advanced civilizationsbeing harnessed by advanced civilizationsand have energy being expended to sustainand have energy being expended to sustainthem, using up most of the radiation energythem, using up most of the radiation energyby having a bunch of absorbers around the star.by having a bunch of absorbers around the star.Dyson first discussed them(1960) and pointed Dyson first discussed them(1960) and pointed

out out that they would be sourcesthat they would be sourcesof intense infra-red radiation due to theof intense infra-red radiation due to thethermal energy output. thermal energy output.



Focused/Directed beam of Focused/Directed beam of neutrinosneutrinos

Why would ETI want to send us a Why would ETI want to send us a focused beam?focused beam?

Don’t know and don’t care! Maybe they Don’t know and don’t care! Maybe they want to get our attention and then want to get our attention and then send us information (e.g. “Beware send us information (e.g. “Beware string theory!” ) Due to long time string theory!” ) Due to long time scales, may remain monologue for a scales, may remain monologue for a while.while.

Many different possibilities: intercept Many different possibilities: intercept signals sent by ETI to their “military” signals sent by ETI to their “military” outposts, we just happen to intercept outposts, we just happen to intercept them…..them…..





Sending a focused beam has the Sending a focused beam has the advantage of not being seen by all, advantage of not being seen by all, and would be less “dangerous”, and would be less “dangerous”, perhaps an advanced ETI wants to perhaps an advanced ETI wants to transmit to a TES(Technologically transmit to a TES(Technologically Emergent Society) like ourselves.Emergent Society) like ourselves.

Perhaps they have been tracking us and Perhaps they have been tracking us and know that we as a TES are ready to know that we as a TES are ready to receive neutrino signals with large KM3 receive neutrino signals with large KM3 detectors?detectors?

Beam choice: electron antineutrinos of Beam choice: electron antineutrinos of energy 6.3 PeV. The cross-section on energy 6.3 PeV. The cross-section on electrons in detectors is large and electrons in detectors is large and characteristic of the Glashow Resonance characteristic of the Glashow Resonance (produce on-shell W with a resultant (produce on-shell W with a resultant shower). No BG and a unique shower). No BG and a unique characteristic energy. characteristic energy.

Range in Water at this energy ~ 100 km Range in Water at this energy ~ 100 km planned detectors will catch ~ 1 % of the planned detectors will catch ~ 1 % of the flux (down-going and horizontal). flux (down-going and horizontal).



Glashow ResonanceGlashow Resonance

When a anti-When a anti-ννe e hits an electron in the hits an electron in the target at an energy of 6.3 PeV(10target at an energy of 6.3 PeV(106 6

GeV),GeV),

the total energy in c.m. is just enuf to the total energy in c.m. is just enuf to

produce a Wproduce a W- - . At this resonant energy . At this resonant energy the cross-section is high and the the cross-section is high and the signal due to the shower of the decay signal due to the shower of the decay of the W is clear………..of the W is clear………..

Such a resonance was first discussed by Glashow in 1960.Such a resonance was first discussed by Glashow in 1960.



--

A possible way to make such A possible way to make such neutrinos is an eneutrinos is an e++-e-e- - Collider in a Collider in a boosted frame with eboosted frame with e- - overtaking the overtaking the ee++, making Z’s of high energy….., making Z’s of high energy…..

From 1 kpc away this beam would be From 1 kpc away this beam would be 3000 AU across, for a pulse of 100 3000 AU across, for a pulse of 100 neutrinos, need 10neutrinos, need 1026 26 neutrinos in the neutrinos in the beam! Again NOT OUR PROBLEM!beam! Again NOT OUR PROBLEM!

A much better choice is a pion A much better choice is a pion accelerator….see e.g. next slide.accelerator….see e.g. next slide.


HonoluluHonolulu 4848Learned, Pakvasa & Zee, Phys. Lett. B 671, 15(2009),arXiv:0805.2429.

Artist’s conception



Protons hitting a target at ~30 PeV, switchable Protons hitting a target at ~30 PeV, switchable between πbetween π++ and π-, decaying into μ and ν and π-, decaying into μ and νμ μ or their or their antiparticles. Muons are removed as in usual beam antiparticles. Muons are removed as in usual beam dumps…A pure νdumps…A pure νμ μ beam, after a few light-days beam, after a few light-days becomes a flavor mixture with νbecomes a flavor mixture with νee:ν:νµµ:ν:ντ τ = 4:7:7.= 4:7:7.

Encoding in a variety of ways: switching back and Encoding in a variety of ways: switching back and forth between neutrinos and antineutrinos, i.e. forth between neutrinos and antineutrinos, i.e. absence or presence of the Glashow Resonance, in absence or presence of the Glashow Resonance, in addition to other signals(muons etc). One can also addition to other signals(muons etc). One can also use timing/pulsing.use timing/pulsing.

Neutrino angle small ~ from 3 kpc, about Neutrino angle small ~ from 3 kpc, about 0.01 AU, much narrower than from Z decay.0.01 AU, much narrower than from Z decay.AGAIN ALL WE HAVE TO DO IS SIT BACK AND WAIT AGAIN ALL WE HAVE TO DO IS SIT BACK AND WAIT FOR SIGNAL OF 6.3 PEV ELECTRON ANTINEUTRINOSFOR SIGNAL OF 6.3 PEV ELECTRON ANTINEUTRINOSIN KM3 DETECTORS………..IN KM3 DETECTORS………..



Neutrinos mix and oscillate.Neutrinos mix and oscillate.

At large distances, oscillations average At large distances, oscillations average out and the only effect is mixing. The out and the only effect is mixing. The propagation matrix is such that an propagation matrix is such that an initiallyinitially

pure pure ννμμ beam becomes a mixture beam becomes a mixture

given by given by ννee::ννµµ::ννττ = 4:7:7 = 4:7:7

Also a beam of Also a beam of ννµ µ produces NO produces NO antineutrinos needed for the Glashow antineutrinos needed for the Glashow resonance. resonance.



Extra SlidesExtra Slides

More on Fermi Question:More on Fermi Question: Many books and articles on this. For Many books and articles on this. For

example: Stephen Webb, “Where is example: Stephen Webb, “Where is everybody?”, Praxis Publishing, 2002.everybody?”, Praxis Publishing, 2002.

Here are listed over 50 proposals for Here are listed over 50 proposals for “solving” the Puzzle listed along with “solving” the Puzzle listed along with counter-arguments.counter-arguments.



Classes of solutions Classes of solutions proposed:proposed:

(1) They are already here!(1) They are already here!

e.g. They are Us, we ARE the aliens!e.g. They are Us, we ARE the aliens!

(2) They exist but have not yet (2) They exist but have not yet communicated…..or don’t want to!communicated…..or don’t want to!

(3) They do not exist!?(3) They do not exist!?



and now for something completely different……

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