BBC: How small is the universe?

Off-topic: Czech police claims to have found the culprits behind the methanol scandal which killed 25 people in recent weeks (and led the government to impose temporary prohibition). The two men have fully confessed and face up to life sentences. A company legally using methanol to produce windshield washers was selling the methanol to the black market. The two criminals knew that they were producing a deadly mixtures of ethanol and methanol – to make profit, regardless of people's lives. I assure everyone that none of this business has ever compromised the safety of Czech exported beverages, especially not those produced near Pilsen, the opposite side of the country, so discrimination against Czech alcohol would be a sign of someone's misunderstanding of the details.

If you haven't watched this BBC2 Horizon program named How small is the universe? four weeks ago, here is the 60-minute video:



Is the narrator speaking in conventional British English?

It's about Nature at very short distance scales and topics such as the string theory landscape, tiny black holes, the Planck length, quasiparticles, MAGIC cosmic rays telescope, and many more things.




The visual effects are pretty good. They probably got much cheaper than a few years ago. Michael Green grows a new universe out of a blue seed in his palm – and many vibrating strings are everywhere, of course. He and others are playing with matryoshka dolls, too.

Well, there are some people I have never heard of, like Joachim Meyer, sorry ;-), despite his cool PICO (or TITAN?) electron microscope which sees individual atoms, rather sharply. They have also been to a cathedral in Aachen. Around 7:00, they start to magnify the matter.

To see inside the atom, they get to the LHC. Andy Parker of ATLAS who "co-built" the device is the guide. He throws some cute old cuckoo clocks from a tower to find out its internal architecture; I was doing similar experiments when I was 7, poor clock. The documentary already treats the Higgs boson discovery as a historical fact. Parker says that his main interest is beyond the higgs, however.

Jeroen van den Brink of Dresden is a solid physicist but he presents his work as looking inside the electron. Well, if you need an example of squalid state physicists' parasiting on the depth of high-energy physics, here you have another one. ;-) So they switch to some X-ray sources that van den Brink, the theorist, doesn't understand, as he admits. At any rate, they create spinons, orbitons, holons, and so on. I am afraid that they deliberately mislead the viewer into thinking that they're observing the splitting of the "fundamental particle". They are just observing an emergent, low-energy effect that "looks like" the particle is being split.

Around 26:40, we return to Parker who wants to create black holes at the LHC so he starts to speak French: impressive. Black holes may only be accessible if there are extra dimensions and gravity is fundamentally stronger than it looks in our superficially 3+1-dimensional world: gravity is leaking into extra dimensions. Parker is driven by his desire to win 3 Nobel prizes – for black holes in the lab, extra dimensions, and falsification of normal GR. ;-)

Michael Green and string theory get to the stage – well, to a French boat – at 33:50. Green's head dissolves into strings. Usual comments about the music of strings. Strings are too small. Strings, if real, are the smallest ones, and at their scale, the notions of big and small turn upside down. 38:00, many solutions, the landscape. The solutions are the peaks, maxima, not minima, in their conventions.

At 41:20, a not-so-physicist is finally given some room. He is not a surfer but a motorbiker. Giovanni Amelino-Camelia tells us that the spacetime is the spacetime. Very interesting. ;-) He says that the BBC viewers are the worst because they think they know a lot but they know nothing: completely nothing. That's still better than Amelino-Camelia's knowledge which is negative. A few vague comments about a discontinuous spacetime at the Planck scale. This babbling by an average Italian in the cafés of Rome made me bored rather quickly.

Hopeless and unjustifiable attempts to find violations of proper relativity via distance gamma ray bursts.

It was an OK program but I would still say that some of the other Horizon episodes discussed on this blog have been better, more informative, based on more special sources, more exciting.

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Are black holes surrounded by firewalls?

Dilaton has noticed a new, extremely provocative concept that was introduced among the quantum gravity researchers two months ago: the firewall.



For decades, people teaching general relativity – including your humble correspondent (e.g. here) – have been explaining that nothing special happens to an infalling observer when she crosses a black hole event horizon. The curvature is usually pretty small there – the curvature radius is close to the black hole radius – and you only get torn apart once you approach the black hole singularity which may be much later.

Advertisement of a future text: Read also Raphael Bousso is right about firewalls

The event horizon is just a coordinate singularity; with a better choice of coordinates, the vicinity of the horizon (including a region below and a region above the horizon) looks like a nearly flat piece of the Minkowski spacetime. These coordinates may be "extremely distorted" functions of some other coordinates you may use for other purposes but they exist. Because the laws of general relativity are local, the (nearly) flat geometry of the region implies that there will be (nearly) the same phenomena there as in the flat space.

Later, some quantum properties of black holes have been pretty much established, too. The picture has made sense to everyone who has ever been considered a top expert in quantum gravity. That was the case until July 2012.




Let me first say what the quantum insights about black holes have been. The black holes evaporate and, as seen in AdS/CFT and Matrix Theory, it's still possible without any violation of the principles of quantum mechanics. So pure states evolve into pure states. From the viewpoint of the observers at infinity, a black hole is just another object with a discrete energy spectrum (well, the levels aren't really sharp because the black hole is unstable: they have a width) that effectively exists outside the event horizon only.

There may be an apparent contradiction between all these things and the validity of the effective field theory for low-energy processes but it's been believed that the contradictions go away because of the "black hole complementarity" paradigm, an opinion that the degrees of freedom (fields) inside the black hole aren't quite independent from those that are outside. They are complicated, scrambled functionals of them.

Now, in mid July 2012, four authors – two of whom are already established as quantum gravity black hole experts you don't want to overlook – published an explosive preprint called

Black Holes: Complementarity or Firewalls?

Joseph Polchinski, Donald Marolf, James Sully, and Ahmed Almheiri – sorry that I sorted the names from the most famous ones – decided to claim that after they have investigated some "detailed models" what happens with the information during the black hole evaporation, they concluded that the usual assumptions are mutually inconsistent, after all.

(See Joe Polchinski's guest blog at Cosmic Variance.)

They considered some thought experiments about entangled qubits that fall into the black hole - constructed out of the \(s\)-wave or other waves in the spherical harmonic decomposition – and decided that the only sensible conclusion is that when a black hole becomes "old" (i.e. when it emits or loses one-half of its initial Bekenstein-Hawking entropy), its event horizon gets transformed into a firewall that destroys everything that gets there.

(If you want to do an experiment, note that you will only be able to say "how you feel" after you cross the event horizon to those people who also fell into a black hole and whose lives are as doomed as yours.)



A song on several observers approaching a firewall. The musician suggests that it's only burning in the observer's eyes.

Within days, an emotional Leonard Susskind replied. The horizon may be kept intact; it's only the singularity of an old black hole that may need a make-up. In another day, Susskind released the second version of the manuscript. Two weeks later, he withdrew the paper because he "no longer believed the argument was right".

A week after the initial provocative paper, Raphael Bousso replied with a rather intelligent paper arguing why Polchinski et al. are wrong. It's clear that Raphael Bousso had to think it was wrong because he's really closer to classical general relativity and Polchinski et al. wanted to question its validity in environments that seem completely mundane! Bousso pointed out that Polchinski et al. were sloppy about the information that various observers, especially the infalling one, may access. When one realizes that they can only evaluate the "causal diamond", all the proofs of contradictions (which typically claim that one may xerox a quantum bit which must be impossible – or which clearly is impossible, depending on your goals – in every consistent quantum theory) become impossible.



Bousso's talk at Strings 2012 about this issue

Daniel Harlow posted another seemingly intelligent reply four days after Bousso. Polchinski et al. were sloppy when they were converting the observations from one observer's reference frame to another. However, Donald Marolf, a co-author of the original paper, kept on fighting and convinced Harlow that there was a hole in his argument. So Harlow withdrew the paper, just like Susskind. The topic of the black hole firewalls surely seems to be a firewall when it comes to burning the actual papers. ;-)



Great Firewall of China, by Ryan McLaughlin

But the fight for freedom and against firewalls continued. Yasunori Nomura, Jaime Varela, and Sean J. Weinberg argued in a way that is somewhat similar to Harlow: one must be careful when she constructs the map between the unitary quantum mechanics with the qubits on one side and the semiclassical world on the other side. The paper exists in the version v3 as well but unlike Harlow's paper, it hasn't been withdrawn yet.

Samir D. Mathur and David Turton "paradoxically" disagree with the firewall, too. I say it's "paradoxical" because Mathur is the father of fuzzballs which also "brutally change" the appearance of the black hole interior. However, they actually believe that the infalling observer has a complementary "nothing happens" description. Their explanation why Polchinski et al. are wrong is seemingly different again: Polchinski et al. assumed that an observer near the event horizon may say lots about the Hawking radiation even if he only looks outside the stretched horizon. Mathur and Turton say that he must actually go all the way to the real horizon and all the answers therefore depend on the Planckian physics.

Borun D. Chowdhury and Andrea Puhm picked catchy words for the same question: Is Alice burning of fuzzing? ;-) Among the followups, they're the closest ones so far to the original paper. They claim that all the critics of Polchinski et al. are just babbling irrelevant nonsense. The only exception are the fuzzball guys from the previous paragraph. Chowdhury and Puhm declare that it's important to get rid of the observer-centric description and talk about decoherence. When it's done, Alice burns when she is a low-energy packet but she may keep on living in the complementary fuzzball picture when she is a high-energy excitation. I suppose that for real people falling into a large, old black hole, this means that they're burned at stake.

In mid August, Leonard Susskind posted a new preprint, unusually similar to the previous one that was withdrawn weeks earlier. It's only the singularity that is modified for an old black hole. However, in the new paper, the evolution of the singularity is rather dramatic because it is – thanks to the growing entanglement – growing towards the event horizon and it ultimately overlaps with it. So Polchinski et al. are right that there's a firewall that burns you at that place; Susskind just says that it's more natural to call it a grown-up singularity, not an event horizon. He at least hopes that this only happens to old black holes (after the Page time, half entropy etc.), not after a much shorter scrambling time (which is just by a logarithmic factor longer than the black hole radius).

The debate wasn't stopped, of course. A day later, Iosif Bena, Andrea Puhm, and Bert Vercnocke formulated the question in yet another way: Non-extremal Black Hole Microstates: Fuzzballs of Fire or Fuzzballs of Fuzz? They take the fuzzball picture as a dogma and try to figure out how the interior looks to an infalling observer. Their conclusions seem inconclusive to me but they surely say lots of general and vacuous things that it could be an important research. ;-)

Amit Giveon and Nissan Itzhaki became supporters of the firewall when they decided to publish a related provocative concept: they think that string theory adds an extra degree of freedom, a zero mode, to the tip of the cigar (the counterpart of the event horizon in simple 1+1-dimensional examples of black holes) relatively to general relativity and this extra degree (or these extra degrees) of freedom may get generalized to a firewall that kills you what you fall into a higher-dimensional black hole.

Tom Banks and Willy Fischler use Tom's somewhat incomprehensible axiomatic framework, the holographic spacetime (I've been exposed to very intensely to as Tom's student), and they conclude that this axiomatic framework doesn't imply any firewalls.

Amos Ori prefers to assume that the semiclassical physics simply has to hold and adjusts any claims about the quantum information as necessary to agree with the primary assumption. With this attitude, he reaches a nearly comparably dramatic conclusion about the black hole information. Most of the information remains trapped throughout most of the evaporation process. Effectively, a small black hole behaves as a black hole remnant.

Ram Brustein wrote so far the most recent followup. The author chooses some very conservative language but arguably proposes a much more radical departure from the lore. The event horizon is a wrong concept; it only exists in the classical theory. In the quantum theory, the black hole's Compton wavelength is nonzero which, the author believes, creates a region near the horizon where the densities are inevitably high and quantum gravity is needed to predict what happens in this new extreme region.

I guess that arXiv.org hasn't hit a firewall yet so new and new followups will keep on emerging.

Your humble correspondent has an opinion what happens but I don't want to extend this cacophony. You must already feel it's crazy. There's surely no consensus here at all and if there were any majority, you would manifestly see that it's irrelevant. The researchers don't seem to agree about anything at all! ;-) Some of the papers are potentially compatible with some of the other papers but you won't find a pair of papers that are really answering the question by Polchinski et al. in equivalent ways.

It's plausible that the reason is that all the questions "what an infalling observer sees and feels" is ill-defined. He may feel "nothing special" but the transformation of the quantum information needed to produce his future state may become arbitrarily contrived once he crosses the horizon, with no need to have any simple relation to perceptions by other observers. After all, extremely singular coordinate transformations are bound to translate to extreme transformations on the Hilbert space, especially if it includes some Planckian degrees of freedom (well, degrees of freedom interpreted as "Planckian" by some of the near-horizon observers). Well, one of the papers above was making a similar point. Perceptions and observations depend on the sensory system's being described by a predictable Hilbert space that reacts in predictable ways. If you can't isolate the Hilbert space that behaves as an "ordinary Hilbert space for the sensory system", it makes no sense to talk about someone's perceptions. (I don't really need to reconstruct eyes; what may get destroyed at the event horizon are much more brute pieces of material, too.) On the other hand, when you redefine the degrees of freedom and evolve them by an ad hoc evolution you would expect outside the black hole, it's not a problem and it won't lead to real contradictions with the things outside because the infalling observer is never going to liberate herself, anyway.

I also think it's problematic to assume that the radiation may be described as a pure state even before the black hole evaporates. The state of the radiation may be obtained by tracing over the interior and the horizon degrees of freedom. Even if the strictly internal degrees of freedom are reshuffled outside degrees of freedom, the influence of the near-horizon degrees of freedom could still make the state of the "radiation only" mixed. One may only be sure about the purity when the black hole is really gone.

Well, I actually think that Polchinski et al. and many others are doing exactly the opposite mistake, too. They think that the radiation is maximally entangled with the black hole so it must be described by a heavily mixed state and can't be maximally entangled with someone else. However, the very point of complementarity, as I understand it, is that the black hole interior's degrees of freedom are just "scrambled copies" of the external ones so you shouldn't double count them (which would be spurious quantum xeroxing). The radiation without the interior is nearly or entirely in a pure state at the Page time! I realize this paragraph says exactly the opposite than the previous one but whichever way it goes, I feel they're not being careful about these important considerations.

At any rate, it surely looks bizarre that the quantum gravity folks can't agree about such a seemingly elementary question, namely the existence and character of the hypothetical firewalls. Many of them are excellent folks but maybe they have focused on too ill-defined questions. Maybe this huge cacophony is a warning sign that the research into these "excessively conceptual" questions got stuck in a swampland observed in a letter by Richard Feynman to his wife after he visited the 1962 conference on (general) relativity in Warsaw:

"I am not getting anything out of the meeting. I am learning nothing. Because there are no experiments, this field is not an active one, so few of the best men are doing work in it. The result is that there are hosts of dopes here (126) and it is not good for my blood pressure. Remind me not to come to any more gravity conferences!"

Are we there again? The black hole interior will always be a mostly inaccessible place for most lucky people so these questions will remain theoretical. But are they meaningful as theoretical questions at all? When you look at the amplitudes that string theory allows you to naturally calculate, such as the S-matrix in various Minkowski spaces, you will find out that the "perceptions of an infalling observer" are not among these calculable things. Maybe string theory has a very good reason why it's trying to hide those would-be observables from us! When I wrote about the reincarnation of the infalling observer, it wasn't quite a joke. I really feel that questions about the infalling observer may be somewhat analogous to various spiritual questions about near-death experiences etc. Some of them may be inaccessible to science – and really ill-defined from a scientific viewpoint.

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EU carbon market will be saved by a new boom of coal

An hour ago, I saw a fascinating article on Patria.CZ, a Czech server for investors, which revealed a highly paradoxical, nearly comical plan.

Analysts at UBS are predicting that by 2015, energy giants such as E.ON and RWE will build lots of new coal power plants – in fact, their capacity will be 6 times greater than the capacity of previously preferred gas-based alternatives. That may send the price of carbon permits up by 73% by 2013. Note that the U.N.-based carbon indulgences' price, CER, dropped by 80 percent in the most recent year.




The new boom that is expected both in Western Europe as well as the post-socialist Europe is the only sensible way how the carbon market may be saved. Isn't it ironic? ;-) For the climate alarmists to preserve their institutionalized bare skin, they must do everything they can to force people to build new coal power plants. Such paradoxical events occur everywhere where planning trumpets the market. The plans – indefensible irrational arbitrary guesses – are almost never right or realistic which is why their champions often have to do many things, including things that manifestly make things worse, to preserve their face.

Note that Europe is already burning coal at the highest rate since 2006 which is great news for the U.S. coal exporters such as Arch Coal Inc.

Joe Romm actually informed us about a closely related insanity. You may now actually earn carbon credits in the "Clean Development Mechanism" if you build new coal power plants! ;-) It's enough for your new power plant to be "supercritical" which really means just some 10% increase of the efficiency. Note that the previous methods to earn the carbon credits were to murder farmers in Honduras and thousands of people in Uganda. So the United Nations support truly "humanitarian" causes.

All these insane games redirect billions of dollars, reduce the efficiency of the markets, and a part of these billions always ends up in the pockets of de facto criminals. Needless to say, the impact on the CO2 emissions is non-existent, not that I would care in one way or another. In fact, the United States that haven't been a party to any carbon credit trading have seen the greatest decrease of CO2 emissions in the world.

Capitalism is an engine that works. Caps, plans, carbon markets, and climate alarmists are dirty sand in between the wheels that tries to stop the engine.

And that's the memo.

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Klaus in Telegraph: on final stages of destruction of democracy in the EU

The Telegraph is running a story on Czech President Klaus' view on the EU and promotes his new book to appear in the U.K. next week,

Václav Klaus warns that the destruction of Europe's democracy may be in its final phase

The book is called The Shattering of Illusions. It has 200 pages and costs £14.44.




Our leader blames two-faced politicians not only in the typical PC parties but also politicians such as the U.K. conservatives for the trend.

The British daily mentions some other worrying statements. Mr Guido Westerwelle, paradoxically from the German FDP, urges the EU to abolish the vetoes of nation states. To enforce the EU law everywhere on the continent, an "EU army" may have to be established. Wow, I haven't heard about it before.

They mention Klaus' criticism of Barroso's recent call for a European federation as well as his longer track record. Klaus agrees that among the European leaders, he is isolated. Many examples of that are listed, e.g. Klaus' recent shocking experience with the Italian politicians who have admitted to be unable to act rationally and who hope that Brussels can do it better. They are escaping responsibility and accountability. David Cameron and his pals are criticized, too. The Tories have mostly lost it in the decades after Thatcher which is why Klaus is closer to UKIP these days.

Klaus finds it paradoxical that it's him who must teach Europe about democracy today.

In the intense discussion below the article, pro-Klaus comments get vastly better ratings than the anti-Klaus comments.

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Australia: qubit as a single silicon atom

Peter F. has pointed out the following intriguing experimental advance in quantum computing:

Australians Create 1-Atom Silicon Quantum Computing Bit (quBit) (Daily Tech)

How does it work?




Well, they take an ordinary single silicon atom, rotate its electron spin (bound to a phosphorus donor atom) in the desired direction by a 1-tesla magnetic field, and then cool it (at least the electrons) down to 0.3 kelvins or so. They're able to manipulate with the electron spin by some clever microwave pulses.



The coherence time is a quarter of a millisecond so far which is pretty good but in their Nature paper,

A single-atom electron spin qubit in silicon,

they hope to get to a second by a tighter control over the phosphorous doping.

Equally optimistically, the electrodes etc. almost look like they are already preparing a commercial implementation of the technology. I believe that if the main element behind classical computers and artificial breasts is used, some if not many existing technologies may be be perhaps recycled to produce a working quantum computer for the first time.

Lazaridis goes into quantum computing

In this article about quantum computing, it may be sensible to point out that they're opening the Mike & Ophelia Lazaridis Quantum-Nano Centre at the University of Waterloo. Links: first, second, third. Hat tip: Joseph S.

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Chu and CMS' Incandela's DOE Higgs talk

Steve Chu is going to get some positive TRF publicity. ;-)



A week ago, Joe Incandela, the boss of CMS, gave a talk for the Department of Energy. Nobel prize winner Steven Chu who happens to be a secretary at the department gave an introduction. In the U.S., you may become a secretary even if you're neither a hot blonde nor a hot brunette.




I think it's a rather neat setup and talk so if you have 80 minutes, you may want to watch it.

Another official's 2-minute pre-introduction is ideological and annoying (clean energy, Fukushima "disaster", and all this rubbish) but you may survive it. Chu is much more sensible. He mentions that Incandela did his thesis on monopoles but what he observed with his three friends at the North Pole turned out to be not so. ;-)

Chu continues with a sketch of modern physics theories. His presentation is a bit more accurate than Bill Clinton's version of these facts.

At the beginning of Incandela's talk, he makes a joke about his string theory colleague in Santa Barbara who told Incandela he was not really interested in the results from the LHC because they only applied to this Universe. ;-) Try to guess the name of the string theorist. I hope that Joe Polchinski hasn't gone this far in the anthropic change of personality!

Incandela talks about masses of particles, the Higgs mechanism etc. but already at 28:00 or so, he gets to supersymmetry and gauge coupling unification, mentioning that it's Edward Witten's most favorite argument in favor of SUSY. Incandela also says that SUSY predicts the right percentage of dark matter, near 25%.

Dark energy will be taxed on one day – a joke emulating Michael Faraday's serious comment – and Incandela proposes a Department of Dark Energy. Well, the left-wingers are ready to tax everything, including CO2 we breathe out, so there's no reason why the cosmological constant should be an exception.

He also gets to extra dimensions and shows his house near the LHC. Comments about the rings near the LHC, temperatures, magnets follow. Construction of the detectors, composition of the collaborations. Newsweek wrote on its cover about the "biggest experiment ever, and it's European". Except that it's a cover of three lies. The picture shows CMS which is not the biggest experiment ever: ATLAS is greater; Americans are welcome; and everything on the picture was made in California. :-)

Bunches of protons, how many. What you create during collisions. Triggers, elimination of events, petabytes to be stored, computer centers. Higgs search in detail, dependence of decay rates on the Higgs mass, Higgs as bump. Bumps growth between 2011 and 2012. P-values for the diphoton and ZZ channels.

The first question at 1:07:00 asks why it's hard to quantize gravity. Incandela seems confused, especially because he hasn't talked about those things at all. So he just says that gravity isn't a part of the Standard Model and it's a task for string theory to include it. Gravity could only be detected with extra dimensions.

Two minutes later, a guy asked a confused question what it means for the bumps to be aligned but he meant bump in the branching ratio charts. Around 1:14:00, Incandela says that some intermediate papers for Kyoto will be published by November (double data) but the triple data will appear in March 2013. Then break.

A question on magnetic monopoles. Everyone used to believe it; ruled out by experiments. No evidence anywhere today. A question and answer on the complementarity and differences between CMS and ATLAS.

At the very end, Chu praises the complexity of the device and also talks about a Christmas present and supersymmetry (which we "desperately" want to see) and compares the energy content of the Swiss chocolate (=the field that a few moments on your lips become years on your hips, funny) and TNT – reaching a clearly wrong result on the latter question, hopefully not the former one. ;-)

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German biogeochemistry postdoc proposes to extinguish the "unsustainable" Sun

Nathaniel Virgo (SE) is a postdoc at the Max Planck Institute for Biochemistry in Jena. His DPhil was about the effect of limited energy supply on organisms. You may see lots of similar "conventional physics" topics that are always "tainted by the environmentalist ideology" a little bit.



Two hours ago, he asked a question at the Physics Stack Exchange that made me LOL. He has already made all the important general plans and only asks the physics users to help him with a technical detail. So his question is:

What is the easiest way to stop a star?

No kidding. You're going to learn something about the mainstream science at the mainstream scientific institutes that do research into Earth sciences. ;-)


-->

What is the easiest way to stop a star?

I'm concerned that the stars are using up hydrogen nuclei at an unsustainable rate. If I was a sufficiently advanced civilisation I might want to do something about this, so that the hydrogen could be burnt in fusion reactors instead. That way, a much higher proportion of the available energy could be put to some use before it eventually becomes thermal radiation.

So my questions are:

1. What would be the most energy-efficient way (using known physics) to blow apart a star or otherwise prevent or greatly slow the rate at which it performs fusion? We're assuming this civilisation has access to vast amounts of energy but doesn't want to waste it unnecessarily, since the aim is to access energy from the hydrogen the star would have burned. In order for this to be worthwhile, the energy gained from doing this would have to be substantially more than the energy the process takes.
2. What would be the astronomical signature of such an activity? If it was happening in a distant galaxy, would we be able to detect it from Earth?

LM:

I emphasized the words "concerned" and "unsustainable" to make it clear that this Gentleman is firmly within the "mainstream" discourse of the Earth sciences that is currently fully controlled by the environmental whackos.

The idea that the Sun wastes too much energy so we should better extinguish it (almost all life on Earth would stop within weeks) is such a funny ramification of the environmentalist thinking (or, more precisely, the absence of it) that I didn't resist and had to repost the question here.

For the sake of completeness, here's my answer:

---

Burning (and fusion) is "unsustainable" by definition because it means to convert an increasing amount of fuel to "energy" plus "waste products" and at some moment, there is no fuel left.

I am not sure whether the word "unsustainable" was used as a joke, a parody of the same nonsensical adjective that is so popular with the low-brow media these days, but I have surely laughed (because it almost sounds like you are proposing to extinguish the Sun to be truly environment-friendly). The thermonuclear reaction in the Sun has been "sustained" for 4.7 billion years and about 7.5 billion years are left before the Sun goes red giant. That's over 10 billion years – many other processes are much less sustainable than that. More importantly, there is nothing wrong about processes' and activities' being "unsustainable". All the processes in the real world are unsustainable and the most pleasant ones are the least sustainable, too.

But back to your specific project.

When it comes to energy, it is possible to blow a star apart without spending energy that exceeds the actual thermonuclear energy stored in the star. Just make a simple calculation for the Sun. Try to divide it to 2 semisuns whose mass is \(10^{30}\) kilograms, each. The current distance between the two semisuns is about \(700,000\) kilometers, the radius of the Sun. You want to separate them to a distance where the potential energy is small, comparable to that at infinity.

It means that you must "liberate" the semisuns from a potential well. The gravitational potential energy you need to spend is\[

E = \frac{G\cdot M\cdot M}{R} = \frac{6.67\times 10^{-11}\times 10^{60}}{700,000,000} =
10^{41}\,{\rm Joules}

\] That's equivalent to the energy of \(10^{24}\) kilograms (the mass of the Moon or so) completely converted to energy via \(E=mc^2\), or thermonuclear energy from burning the whole Earth of hydrogen (approximately).

You may force the Sun to do something like the "red giant" transition prematurely and save some hydrogen that is unburned. To do so, you will have to spend the amount of energy corresponding to the Earth completely burned via fusion.

But of course, the counting of the energy which was "favorable" isn't the only problem. To actually tear the Sun apart, you would have to send an object inside the Sun that would survive the rather extreme conditions over there, including 15 million Celsius degrees and 3 billion atmospheres of pressure. Needless to say, no solid can survive these conditions: any object based on atoms we know will inevitably become a plasma. A closely related fact is that ordinary matter based on nuclei and electron doesn't allow for any "higher-pressure" explosion than the thermonuclear one so there's nothing "stronger" that could be sent to the Sun as an explosive to counteract the huge pressure inside the star.

One must get used to the fact that plasma is what becomes out of anything that tries to "intervene" into the Sun – and any intruder would be quickly devoured and the Sun would restore its balance. The only possible loophole is that the amount of this stuff is large. So you may think about colliding two stars which could perhaps tear them apart and stop the fusion. This isn't easy. The energy needed to substantially change the trajectory of another star is very, very large, unless one is lucky that the stars are already going to "nearly collide" which is extremely unlikely.

Physics will not allow you to do such things. You would need a form of matter that is more extreme than the plasma in the Sun, e.g. the neutron matter, but this probably can't be much lighter (and easier to prepare, e.g. when it comes to energy) than the star itself. A black hole could only drill a hole (when fast enough) or consume the Sun (which you don't want).

However, if you allow the Sun to be eaten by a black hole, you will actually get a more efficient and more sustainable source of energy. Well, too sustainable. ;-) A black hole of the mass comparable to the solar mass would have a radius about 3 miles. It would only send roughly one photon of the 3-mile-long wavelength every nanosecond or so in the Hawking radiation and it would only evaporate after \(10^{60}\) years or so. It would be so sustainable that no one could possibly observe the energy it is emitting. However, the black hole would ultimately emit all the energy \(E=mc^2\) stored in the mass.

If there are powerful civilizations ready to do some "helioengineering", they surely don't suffer from naive and primitive misconceptions about the world such as the word "sustainable" and many other words that are so popular in the mentally retarded movement known as "environmentalism". These civilizations may do many things artificially but they surely realize that the thermonuclear reaction in the stars is a highly efficient and useful way to get the energy from the hydrogen fuel. Even some of us realize that almost all the useful energy that allowed the Earth to evolve and create life and other things came from the Sun.

The Sun may become unsustainable in 7.5 billion years but according to everything we know about Nature, it's the optimum device to provide large enough civilizations – whole planets – with energy.

Concerning ambitious but less crazy plans in the outer space, look at NASA's plans to produce a "warp drive": HTML, PDF.

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