Monday, August 30, 2021

Finitism and Physics

New paper on arXiv today.

A brief precis: Gravitational collapse limits the amount of energy present in any space-time region. This in turn limits the precision of any measurement or experimental process that takes place in the region. This implies that the class of models of physics which are discrete and finite (finitistic) cannot be excluded experimentally by any realistic process. Note any digital computer simulation of physical phenomena is a finitistic model.

We conclude that physics (Nature) requires neither infinity nor the continuum. For instance, neither space-time nor the Hilbert space structure of quantum mechanics need be absolutely continuous. This has consequences for the finitist perspective in mathematics -- see excerpt below.
Fundamental Limit on Angular Measurements and Rotations from Quantum Mechanics and General Relativity 
arXiv:2108.11990 
Xavier Calmet, Stephen D.H. Hsu 
We show that the precision of an angular measurement or rotation (e.g., on the orientation of a qubit or spin state) is limited by fundamental constraints arising from quantum mechanics and general relativity (gravitational collapse). The limiting precision is 1/r in Planck units, where r is the physical extent of the (possibly macroscopic) device used to manipulate the spin state. This fundamental limitation means that spin states S1 and S2 cannot be experimentally distinguished from each other if they differ by a sufficiently small rotation. Experiments cannot exclude the possibility that the space of quantum state vectors (i.e., Hilbert space) is fundamentally discrete, rather than continuous. We discuss the implications for finitism: does physics require infinity or a continuum?

From the conclusions:

IV. FINITISM: DOES PHYSICS REQUIRE A CONTINUUM? 
Our intuitions about the existence and nature of a continuum arise from perceptions of space and time [21]. But the existence of a fundamental Planck length suggests that spacetime may not be a continuum. In that case, our intuitions originate from something (an idealization) that is not actually realized in Nature. 
Quantum mechanics is formulated using continuous structures such as Hilbert space and a smoothly varying wavefunction, incorporating complex numbers of arbitrary precision. However beautiful these structures may be, it is possible that they are idealizations that do not exist in the physical world. 
The introduction of gravity limits the precision necessary to formulate a model of fundamental quantum physics. Indeed, any potential structure smaller than the Planck length or the minimal angle considered here cannot be observed by any device subject to quantum mechanics, general relativity, and causality. Our results suggest that quantum mechanics combined with gravity does not require a continuum, nor any concept of infinity. 
It may come as a surprise to physicists that infinity and the continuum are even today the subject of debate in mathematics and the philosophy of mathematics. Some mathematicians, called finitists, accept only finite mathematical objects and procedures [25]. The fact that physics does not require infinity or a continuum is an important empirical input to the debate over finitism. For example, a finitist might assert (contra the Platonist perspective adopted by many mathematicians) that human brains built from finite arrangements of atoms, and operating under natural laws (physics) that are finitistic, are unlikely to have trustworthy intuitions concerning abstract concepts such as the continuum. These facts about the brain and about physical laws stand in contrast to intuitive assumptions adopted by many mathematicians. For example, Weyl (Das Kontinuum [21, 22]) argues that our intuitions concerning the continuum originate in the mind’s perception of the continuity of space-time. 
There was a concerted effort beginning in the 20th century to place infinity and the continuum on a rigorous foundation using logic and set theory. However, these efforts have not been successful. For example, the standard axioms of Zermelo-Fraenkel (ZFC) set theory applied to infinite sets lead to many counterintuitive results such as the Banach-Tarski Paradox: given any two solid objects, the cut pieces of either one can be reassembled into the other [23]. When examined closely all of the axioms of ZFC (e.g., Axiom of Choice) are intuitively obvious if applied to finite sets, with the exception of the Axiom of Infinity, which admits infinite sets. (Infinite sets are inexhaustible, so application of the Axiom of Choice leads to pathological results.) The Continuum Hypothesis, which proposes that there is no cardinality strictly between that of the integers and reals, has been shown to be independent (neither provable nor disprovable) in ZFC [24]. Finitists assert that this illustrates how little control rigorous mathematics has on even the most fundamental properties of the continuum. 
David Deutsch [26]: The reason why we find it possible to construct, say, electronic calculators, and indeed why we can perform mental arithmetic, cannot be found in mathematics or logic. The reason is that the laws of physics “happen to” permit the existence of physical models for the operations of arithmetic such as addition, subtraction and multiplication. 
This suggests the primacy of physical reality over mathematics, whereas usually the opposite assumption is made. From this perspective, the parts of mathematics which are simply models or abstractions of “real” physical things are most likely to be free of contradiction or misleading intuition. Aspects of mathematics which have no physical analog (e.g., infinite sets, the continuum) are prone to problems in formalization or mechanization. Physics – i.e., models which can be compared to experimental observation, actual “effective procedures” – does not ever require infinity, although it may be of some conceptual convenience. Hence it seems possible, and the finitists believe, that the Axiom of Infinity and its equivalents do not provide a sound foundation for mathematics.
See also 

We experience the physical world directly, so the highest confidence belief we have is in its reality. Mathematics is an invention of our brains, and cannot help but be inspired by the objects we find in the physical world. Our idealizations (such as "infinity") may or may not be well-founded. In fact, mathematics with infinity included may be very sick, as evidenced by Godel's results, or paradoxes in set theory. There is no reason that infinity is needed (as far as we know) to do physics. It is entirely possible that there are only a (large but) finite number of degrees of freedom in the physical universe.
Paul Cohen: I will ascribe to Skolem a view, not explicitly stated by him, that there is a reality to mathematics, but axioms cannot describe it. Indeed one goes further and says that there is no reason to think that any axiom system can adequately describe it.
This "it" (mathematics) that Cohen describes may be the set of idealizations constructed by our brains extrapolating from physical reality. But there is no guarantee that these idealizations have a strong kind of internal consistency and indeed they cannot be adequately described by any axiom system.



Note added
: I should clarify the paragraph from our paper that begins
There was a concerted effort beginning in the 20th century to place infinity and the continuum on a rigorous foundation using logic and set theory. However, these efforts have not been successful. ...
This refers to Hilbert's Program:
In the early 1920s, the German mathematician David Hilbert (1862–1943) put forward a new proposal for the foundation of classical mathematics which has come to be known as Hilbert’s Program. It calls for a formalization of all of mathematics in axiomatic form, together with a proof that this axiomatization of mathematics is consistent. The consistency proof itself was to be carried out using only what Hilbert called “finitary” methods. The special epistemological character of finitary reasoning then yields the required justification of classical mathematics. Although Hilbert proposed his program in this form only in 1921, various facets of it are rooted in foundational work of his going back until around 1900, when he first pointed out the necessity of giving a direct consistency proof of analysis. ...
which Godel showed is not possible to carry out. Note that one of Hilbert's main motivations was the continuum (e.g., construction of the Reals in analysis). What has subsequently been adopted as the rigorous basis for analysis does not satisfy Hilbert's desire for axiomatic, finitary methods. 

The remaining sentences in the paragraph are meant to elucidate aspects of the modern treatment that its critics find unappealing. Of course, judgements of this type are philosophical in nature. 
... For example, the standard axioms of Zermelo-Fraenkel (ZFC) set theory applied to infinite sets lead to many counterintuitive results such as the Banach-Tarski Paradox: given any two solid objects, the cut pieces of either one can be reassembled into the other [23]. When examined closely all of the axioms of ZFC (e.g., Axiom of Choice) are intuitively obvious if applied to finite sets, with the exception of the Axiom of Infinity, which admits infinite sets. (Infinite sets are inexhaustible, so application of the Axiom of Choice leads to pathological results.) The Continuum Hypothesis, which proposes that there is no cardinality strictly between that of the integers and reals, has been shown to be independent (neither provable nor disprovable) in ZFC [24]. Finitists assert that this illustrates how little control rigorous mathematics has on even the most fundamental properties of the continuum. 

Friday, August 27, 2021

Tragedy of Empire / Mostly Sociopaths at the Top

 

Ecclesiastes 1:9 (KJV) The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun.

Turn off the TV and close the browser tabs with mainstream media content produced by middlebrow conformists. Watch this video instead and read the links below. 

If you were surprised by events in Afghanistan over the past weeks, ask yourself why you were so out of touch with a reality that has been clear to careful observers for over a decade. Then ask yourself what other things you are dead wrong about...

Ray McGovern is a retired CIA analyst who served as Chief of the Soviet Foreign Policy Branch and preparer/briefer of the President’s Daily Brief. Prior to that he served as an infantry/intelligence officer in the 1960s. 

McGovern wrote Welcome to Vietnam, Mr. President (addressed to President Obama, about Afghanistan) in 2009. 

See also: The Strategic Lessons Unlearned from Vietnam, Iraq, and Afghanistan: Why the Afghan National Security Forces Will Not Hold, and the Implications for the U.S. Army in Afghanistan (Strategic Studies Institute and U.S. Army War College Press 2015) M. Chris Mason  

Related posts:

Tears before the Rain: An Oral History of the Fall of South Vietnam (Afghanistan darkness over Kabul edition) 



Afghanistan is lost (2012)




Podcast version of the interview at top:
   



More color here from Danny Sjursen, West Point graduate, former US Army Major. Sjursen is a combat veteran who served in Iraq and later as an Army Captain in Afghanistan in command of 4-4 Cavalry B Troop in Kandahar Province from February 2011 to January 2012.




Added from comments:
At the strategic level it has been clear for 10+ years that our resources were better used elsewhere. It was obvious as well that we were not succeeding in nation building or creating a self-sustaining government there. I could go into more detail but you can get it from the links / interviews in the post. 
At the tactical level it should have been obvious that a quick collapse was very possible, just as in S. Vietnam (see earlier oral history post). Off-topic: same thing could happen in Taiwan in event of an actual invasion, but US strategists are clueless. 
Biden deserves credit for staying the course and not kicking the can down the road, as effectively a generation (slight exaggeration) of military and political leaders have done. 
The distortion of the truth by senior leaders in the military and in politics is clear for all to see. Just read what mid-level commanders (e.g., Sjursen) and intel analysts with real familiarity have to say. This was true for Vietnam and Iraq as well. Don't read media reports or listen to what careerist generals (or even worse, politicos) have to say. 
Execution by Biden team was terrible and I think they really believed the corrupt US-puppet Afghan govt could survive for months or even years (i.e., they are really stupid). Thus their exit planning was deeply flawed and events overtook them. However, even a well-planned exit strategy would likely not have avoided similar (but perhaps smaller in magnitude) tragic events like the ones we are seeing now. 
ISS attack on airport was 100% predictable. I don't think most Americans (even "leaders" and "experts") understood ISS and Taliban are mortal enemies, etc. etc. 
There is more of a late-stage imperial decline feel to Afghanistan and Iraq -- use of mercenaries, war profiteering, etc. -- than in Vietnam. All of these wars were tragic and unnecessary, but there really was a Cold War against an existential rival. The "war on terrorism" should always have been executed as a police / intel activity, not one involving hundreds of thousands of US soldiers. 
All of this is (in part) an unavoidable cost of having intellectually weak leaders struggling with difficult problems, while subject to low-information populist democracy (this applies to both parties and even to "highly educated" coastal elites; the latter are also low-information from my perspective). This situation is only going to get worse with time for the US. 
BTW, I could describe an exactly analogous situation in US higher ed (with which I am quite familiar): leaders are intellectually weak, either do not understand or understand and cynically ignore really serious problems, are mainly concerned with their own careers and not the real mission goals, are subject to volatility from external low-information interest groups, etc.

Wednesday, August 25, 2021

Resistance fighter negotiates with former torturer (Afghanistan edition)


The Taliban could easily turn Kabul airport into a trap, creating another Dien Bien Phu for the US. However I suspect they are advised by the Russians and Chinese to grant the Americans a peaceful exit from their 20 year disaster. The negotiations are presumably about the ~$9 billion of frozen assets in the Afghanistan treasury, future sanctions against a Taliban-led government, etc.

CIA Director William Burns held secret meeting in Kabul with Taliban leader Abdul Ghani Baradar (WaPo) 
President Biden dispatched his top spy, a veteran of the Foreign Service and the most decorated diplomat in his Cabinet, amid a frantic effort to evacuate people from Kabul international airport in what Biden has called “one of the largest, most difficult airlifts in history.” 
The CIA declined to comment on the Taliban meeting, but the discussions are likely to have involved an impending Aug. 31 deadline for the U.S. military to conclude its airlift of U.S. citizens and Afghan allies. The Biden administration is under pressure from some allies to keep U.S. forces in the country beyond the end of the month to assist the evacuation of tens of thousands of citizens of the United States and Western countries as well as Afghan allies desperate to escape Taliban rule. 
Britain, France and other U.S. allies have said more time is needed to evacuate their personnel, but a Taliban spokesman warned that the United States would be crossing a “red line” if it kept troops beyond the 31st, which he said would trigger unspecified “consequences.” 
For Baradar, playing the role of counterpart to a CIA director comes with a tinge of irony 11 years after the spy agency arrested him in a joint CIA-Pakistani operation that put him in prison for eight years. ...

There are many more like Baradar. Taliban leader Gholam Ruhani (circled in the photo at top) enjoyed America's tender embrace for many years at Guantanamo.  


I highly recommend The Battle of Algiers for context, as did the Pentagon in 2003 -- to no avail.


Wikipedia
The highly dramatic film is about the organization of a guerrilla movement and the illegal methods, such as torture, used by the colonial power to contain it. Algeria succeeded in gaining independence from the French, which Pontecorvo addresses in the film's epilogue.[3] 
The film has been critically acclaimed. Both insurgent groups and state authorities have considered it to be an important commentary on urban guerrilla warfare. 
2003 Pentagon screening 
During 2003, the press reported that United States Department of Defense (the Pentagon) offered a screening of the movie on August 27. The Directorate for Special Operations and Low-Intensity Conflict regarded it as useful for commanders and troops facing similar issues in occupied Iraq.[38] 
A flyer for the screening said: How to win a battle against terrorism and lose the war of ideas. Children shoot soldiers at point-blank range. Women plant bombs in cafes. Soon the entire Arab population builds to a mad fervor. Sound familiar? The French have a plan. It succeeds tactically, but fails strategically. To understand why, come to a rare showing of this film.[39] 
According to the Defense Department official in charge of the screening, "Showing the film offers historical insight into the conduct of French operations in Algeria, and was intended to prompt informative discussion of the challenges faced by the French."[39]
Re: Dien Bien Phu, colonial wars, and Iraq / Afghanistan:
General Georges Catroux presided over a commission of inquiry into the defeat. The commission's final report ("Rapport concernant la conduite des opérations en Indochine sous la direction du général Navarre") concluded: 
"... The event itself was in fact, both in terms of public opinion and of the military conduct of the war and operations, merely the end result of a long process of degradation of a faraway enterprise which, not having the assent of the nation, could not receive from the authorities the energetic impulse, and the size and continuity of efforts, required for success. ..."

Tuesday, August 17, 2021

John Preskill interview by Sean Carroll

 

This is a great interview of John Preskill by Sean Carroll. 

Both are many worlders. At about 20 minutes John says:
I'm an Everettian... 
I'm comfortable with nothing happening in the world besides unitary evolution ... 
Measurement isn't something fundamentally different. ... 
It seems minimal: you know there's nothing happening but the Schrodinger equation and things are evolving, and if we can reconcile that with what we observe about physics ...

In Ten Years of Quantum Coherence and Decoherence I listed a number of prominent theorists who have expressed some degree of belief in many worlds.

Q1. (largely mathematical): Does the phenomenology of pure state evolution in a closed system (e.g., the universe) reproduce Copenhagen for observers in the system? 
This is a question about dynamical evolution: of the system as a whole, and of various interacting subsystems. It's not a philosophical question and, in my opinion, it is what theorists should focus on first. Although complicated, it is still reasonably well-posed from a mathematical perspective, at least as far as foundational physics questions go. 
I believe the evidence is strong that the answer to #1 is Yes, although the issue of the Born rule lingers (too complicated to discuss here, but see various papers I have written on the topic, along with other people like Deutsch, Zurek, etc.). It is clear from Weinberg's writing that he and I agree that the answer is Yes, modulo the Born rule. 
Define this position to be 
Y* := "Yes, possibly modulo Born" 
There are some theorists who do not agree with Y* (see the survey results above), but they are mostly people who have not thought it through carefully, in my opinion. 
I don't know of any explicit arguments for how Y* fails, and our recent results applying the vN QET strengthen my confidence in Y*. 
I believe (based on published remarks or from my personal interactions) that the following theorists have opinions that are Y* or stronger: Schwinger, DeWitt, Wheeler, Deutsch, Hawking, Feynman, Gell-Mann, Zeh, Hartle, Weinberg, Zurek, Guth, Preskill, Page, Cooper (BCS), Coleman, Misner, Arkani-Hamed, etc. 
But there is a generational issue, with many older (some now deceased!) theorists being reticent about expressing Y* even if they believe it. This is shifting over time and, for example, a poll of younger string theorists or quantum cosmologists would likely find a strong majority expressing Y*. 
[ Social conformity and groupthink are among the obstacles preventing broader understanding of Q1. That is, in part, why I have listed specific high profile individuals as having reached the unconventional but correct view! ]

Saturday, August 14, 2021

Tears before the Rain: An Oral History of the Fall of South Vietnam (Afghanistan darkness over Kabul edition)

Ecclesiastes 1:9 (KJV) The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun.

If you are following events in Afghanistan you know that the tragedy described below will soon be repeated.

The oral histories collected in this volume are heartbreaking and real, but today the events they describe are all but forgotten.

There was never any reckoning for the crimes and stupidity of the Vietnam war, and there won't be any in the wake of our 20 years in Afghanistan and Iraq. 

Our pathetic leaders and apathetic voters will find plenty of other things to distract them from a serious consideration of what happened. Strike up the band, and salute the flag.


Saigon, US Embassy evacuation, 29 April, 1975:

Kabul, US Embassy evacuation, 15 August, 2021:

From the introduction:

On March 10, 1975, the North Vietnamese Army launched what was to be its final major offensive against South Vietnam, assured that America had lost its will to fight or to finance the independence of South Vietnam. No longer fearful of American intervention, the North Vietnamese were certain that victory and the forceful unification of Vietnam was, after nearly thirty years of conflict, soon to be accomplished. Now the social and military fabric of South Vietnam began to unravel rapidly in many places at the same time. The South suddenly began to lose the war faster than the North could win it. The military forces of the South seemed to be imploding toward Saigon. Cities and provinces were abandoned to the North without a fight. ...Victory for the armies of North Vietnam became, in many strategically important places, a mere matter of marching. 
On March 29, the chaotic and desperate situation was recorded graphically by a CBS news crew that flew aboard a World Airways Boeing 727 to Danang, Vietnam's second largest city, to evacuate refugees. The plane was mobbed by soldiers who shot women and children and each other in a frenzied attempt to scramble aboard the aircraft and escape from the advancing North Vietnamese. As the plane took off with people clinging to the wheels, soldiers on the ground fired at it and a hand grenade blew up under one wing. The plane limped back into Saigon, and that evening a tape of the flight was shown on the CBS Evening News. American television viewers that Easter weekend saw the almost unbelievable horror of an army transformed into murderous rabble and a country thrashing about helplessly in the throes of a violent death. 
... As if to leave no doubt as to America's determination not to intervene again in Vietnam, on the evening of April 23, in a major address at Tulane University, President Gerald Ford announced that the war in Vietnam was "finished as far as America is concerned." The audience of students gave him a standing ovation. 
... On the morning of April 29, Operation Frequent Wind began. The exercise involved the evacuation of American and Vietnamese civilians and military personnel from Tan Son Nhut Airbase and from the American Embassy in Saigon to the Seventh Fleet in the South China Sea. The operation was completed early in the morning of April 30, a few hours before the surrender of the South. When the last Marines were airlifted from the roof of the American Embassy on the morning of April 30, they left behind more than four hundred Vietnamese waiting to be airlifted out of the compound. Throughout the previous day and night those same Vietnamese had been promised again and again that they would never be abandoned by the United States. They watched in silence as the last American helicopter left the roof of the Embassy. Even the final American promise to Vietnam had been broken.
Thomas Polgar was CIA Saigon station chief. This is his last transmission from the embassy before destroying the communications equipment:
“This will be final message from Saigon station,” Mr. Polgar wrote. “It has been a long and hard fight and we have lost. This experience, unique in the history of the United States, does not signal necessarily the demise of the United States as a world power. 
“The severity of the defeat and the circumstances of it, however, would seem to call for a reassessment... Those who fail to learn from history are forced to repeat it. Let us hope that we will not have another Vietnam experience and that we have learned our lesson.”
From his oral history:
... we got word to go, and the ambassador was finally told, ... "No, it's going to be from the roof after all." ...
I didn't have a great emotional attachment to Vietnam like some of my colleagues who really fell in love with the country. But in the end, seeing how it ended, I thought that we really did a miserable job for these people and they would have been much better off if we had never gone there in the first place. 
Our reception on the Blue Ridge [ship] showed the American military at its worst. They started out by searching everybody. I think the ambassador was the only one who was not searched. And in normal peacetime I far outranked the admiral commanding the ship. Nobody objected, though. We were tired. We were pretty placid. And we were a defeated army.
From the epigraph:
Maybe if enough people know what happened to Vietnam, then my memories will never be lost. Maybe then they will be like tears before the rain. So listen. This is very important. This is what I remember. This is what happened to me. These are my tears before the rain. --Duong Gang Son
More from Son's oral history:
As we left Saigon, there was an American soldier standing at the back door of the plane, and he was shooting at the ground. He just kept shooting as we pulled away. And people were still crying inside the plane. I watched the soldier shooting and I wondered what he was shooting at. I think he was just trying to show American power one last time. ... But I can only guess. I don't think he knew what was happening, either. We were all confused. 
Anyway, that was my last look at my country. I saw Vietnam as we flew away and at the back door of the plane was a soldier with a gun shooting at it.

 

Tears before the Rain: An Oral History of the Fall of South Vietnam by Larry Engelmann 

CBS camera-man Mike Marriott was on the last plane to escape from Danang before it fell in the spring of 1975. The scene was pure chaos: thousands of panic-stricken Vietnamese storming the airliner, soldiers shooting women and children to get aboard first, refugees being trampled to death. Marriott remembers standing at the door of the aft stairway, which was gaping open as the plane took off. "There were five Vietnamese below me on the steps. As the nose of the aircraft came up, because of the force and speed of the aircraft, the Vietnamese began to fall off. One guy managed to hang on for a while, but at about 600 feet he let go and just floated off--just like a skydiver.... What was going through my head was, I've got to survive this, and at the same time, I've got to capture this on film. This is the start of the fall of a country. This country is gone. This is history, right here and now." 

In Tears Before the Rain, a stunning oral history of the fall of South Vietnam, Larry Engelmann has gathered together the testimony of seventy eyewitnesses (both American and Vietnamese) who, like Mike Marriott, capture the feel of history "right here and now." We hear the voices of nurses, pilots, television and print media figures, the American Ambassador Graham Martin, the CIA station chief Thomas Polgar, Vietnamese generals, Amerasian children, even Vietcong and North Vietnamese soldiers. 

Through this extraordinary range of perspectives, we experience first-hand the final weeks before Saigon collapsed, from President Thieu's cataclysmic withdrawal from Pleiku and Kontum, (Colonel Le Khac Ly, put in command of the withdrawal, recalls receiving the order: "I opened my eyes large, large, large. I thought I wasn't hearing clearly") to the last-minute airlift of Americans from the embassy courtyard and roof ("I remember when the bird ascended," says Stuart Herrington, who left on one of the last helicopters, "It banked, and there was the Embassy, the parking lot, the street lights. And the silence"). 


Kabul Update
: right on schedule...

See also Decline of the American Empire: Afghan edition (stay tuned for more).

Wednesday, August 11, 2021

Ten Years of Quantum Coherence and Decoherence


In 2010 I attended a meeting on Quantum Coherence and Decoherence in Benasque, Spain. I've reproduced part of my original blog post on the meeting below.

 

September 13, 2010  
Here are the slides for my talk today at Benasque: On the origin of probability in quantum mechanics.

At the end I took a poll of the workshop participants and found that over half agreed with the following statement. About 20 percent were strongly opposed. Note this is a meeting on quantum coherence and decoherence, so there are a lot of practical types here, including experimentalists.

It is plausible (but of course unproven) that unitary evolution of a pure state in a closed system can reproduce, for semi-classical creatures inside the system, all of the phenomenology of the Copenhagen interpretation.

As one insightful participant pointed out while I was taking the poll, this is really a mathematical question (if not entirely well-posed), not a physics question.

My recent paper with Roman Buniy: Macroscopic Superpositions in Isolated Systems answers the mathematical question about the dynamics of complex isolated systems under Schrodinger evolution. I had forgotten entirely about the poll in the intervening years (I only came across the blog post by accident recently), but the question persisted... Only in 2020 did I realize that von Neumann's Quantum Ergodic Theorem [1] [2] can be used to prove the result.



Some Benasque photos from 2010 :-)







Added from comments

There are really multiple issues here. Theorists will differ in their opinions on the following questions: 
 
1. (largely mathematical): Does the phenomenology of pure state evolution in a closed system (e.g., the universe) reproduce Copenhagen for observers in the system? 

This is a question about dynamical evolution: of the system as a whole, and of various interacting subsystems. It's not a philosophical question and, in my opinion, it is what theorists should focus on first. Although complicated, it is still reasonably well-posed from a mathematical perspective, at least as far as foundational physics questions go. 

I believe the evidence is strong that the answer to #1 is Yes, although the issue of the Born rule lingers (too complicated to discuss here, but see various papers I have written on the topic, along with other people like Deutsch, Zurek, etc.). It is clear from Weinberg's writing that he and I agree that the answer is Yes, modulo the Born rule. 

Define this position to be 

Y* := "Yes, possibly modulo Born" 

There are some theorists who do not agree with Y* (see the survey results above), but they are mostly people who have not thought it through carefully, in my opinion. I don't know of any explicit arguments for how Y* fails, and our recent results applying the vN QET strengthen my confidence in Y*. 

I believe (based on published remarks or from my personal interactions) that the following theorists have opinions that are Y* or stronger: Schwinger, DeWitt, Wheeler, Deutsch, Hawking, Feynman, Gell-Mann, Zeh, Hartle, Weinberg, Zurek, Guth, Preskill, Page, Cooper (BCS), Coleman, Misner, Arkani-Hamed, etc. 

But there is a generational issue, with many older (some now deceased!) theorists being reticent about expressing Y* even if they believe it. This is shifting over time and, for example, a poll of younger string theorists or quantum cosmologists would likely find a strong majority expressing Y*. 

[ Social conformity and groupthink are among the obstacles preventing broader understanding of question #1. That is, in part, why I have listed specific high profile individuals as having reached the unconventional but correct view! ]


2. Does this make you confident that the other branches really "exist"? They are "real"? 

Here we get into philosophical questions and you will get a range of answers. 

Many of the Y* theorists (including me) might say:

a. MW is the only logically complete version of QM we have. Copenhagen is not well-defined and inadequate for cosmology (cf density perturbations from inflation and galaxy formation). 

b. I find the existence of the other branches rather extravagant, and I leave open the possibility that there might be some more fundamental modification of QM that changes everything. But I have no idea what that model looks like and there are strong constraints on its properties from Bell, causality, etc. Even a small amount of nonlinearity in the Schrodinger equation leads to lots of causality violation, etc. etc. 
 
c. I believe that any practical experiment that tries to check whether unitary evolution always holds (i.e., the other branches are *in principle accessible*) will always find it to be the case. In particular this means we will realize and manipulate more and more complicated superposition states over time, and this raises the question of why you and I cannot be in a superposition state right now... 

Note it is possible that only one single decoherent branch of the universal wavefunction is actually realized by Nature ("is real"), and that quantum randomness is an illusion. Hartle and Gell-Mann were sort of hedging this way in some of their last papers on this topic. But remember Gell-Mann even hedged about the reality of quarks before they were directly observed in deep inelastic scattering. 

An aspect to this problem that few theorists appreciate is that a quantum theory of gravity is, at the global level, "timeless": it should be a theory of quantum amplitudes describing an entire spacetime geometry and quantum trajectories of other degrees of freedom on that manifold. As such the many branches of the universal wavefunction are realized "all at once" and concepts like observers must be emergent -- they cannot be fundamental aspects of the theory itself. 

Most of the action in quantum gravity (i.e., strings or loop qg) has been "local" in nature: what are the stringy excitations, compactification, local vacua, etc. The global wavefunction of the universe was already considered by Wheeler and DeWitt but there are still lots of unresolved issues.

Friday, August 06, 2021

Strategic Calculus of a Taiwan Invasion



It seems implausible to me that PRC would risk an invasion of Taiwan in the near term, absent a very strong provocation such as an outright declaration of independence. Mastro's recent article in Foreign Affairs: China's Taiwan Temptation made the case for potential near term conflict, and caused quite a stir among analysts.

My guess is that PRC already has the capability to take Taiwan, but not without significant risk. However, as long as they continue to believe that time is on their side an invasion seems unlikely.

Some comments:

1. PRC would have local air and naval superiority at the beginning of the conflict.

2. I am uncertain as to the details of lift/amphibious assault -- discussed by Goldstein on the panel. This is the main failure mode for PLA.

3. I am uncertain as to Taiwan's will to fight. A quick surrender is not excluded, in my opinion. It seems that most US planners do not understand this.

4. Most westerners fail to understand that this is a frozen civil war, with very strong and emotional commitments from the PRC side. The involvement of Japan in this conflict, given their history of aggression in Asia and previous colonial occupation of Taiwan, could easily get them nuked again (this time with much greater megatonnage). It is unclear whether the present leadership of Japan appreciates this sufficiently.

5. The interests of the average person in the US or Japan (or any Asian country) are best served by working very hard to avoid this conflict.

What is happening across the Taiwan Strait? 
In March, Admiral Philip Davidson, then commander of U.S. forces in the Pacific (INDOPACOM), said in a hearing before Congress that a Chinese attack on Taiwan could take place within six years. His successor, Admiral John Aquilino, agreed that such an attack could occur sooner “than most think.” More recently, however, the chairman of the joint chiefs of staff, General Mark Milley, testified that he believes that China has little intention to take Taiwan by force, and that the capability to do so remains a goal rather than a reality. 
On the other hand, the Chinese military has increased pressure on Taiwan in the past year, flying into the island’s air defense identification zone on numerous occasions. During one day in June, China flew 28 military aircraft toward Taiwan, the largest number in a single day, perhaps in response to G7 and NATO statements on China and Taiwan. 
On July 19, 2021, the National Committee hosted a virtual program with Lyle Goldstein and Oriana Skylar Mastro to discuss China/Taiwan/U.S. military relations. NCUSCR President Stephen Orlins moderated and NCUSCR Director Admiral Dennis Blair offered commentary. 
Lyle J. Goldstein is a research professor in the China Maritime Studies Institute (CMSI) at the Naval War College (NWC) and an affiliate of its new Russia Maritime Studies Institute. Founding director of CMSI and author of dozens of articles on Chinese security policy, he focuses on Chinese undersea warfare. On the broader subject of U.S.-China relations, Dr. Goldstein published Meeting China Halfway in 2015. Over the last several years, he has focused on the North Korea crisis. 
Dr. Goldstein received his bachelor’s degree in government from Harvard, his master’s degree in strategic studies and international economics from the Johns Hopkins University School of Advanced International Studies, and his doctoral degree in politics from Princeton. He speaks Russian as well as Chinese. 
Oriana Skylar Mastro is a center fellow at the Freeman Spogli Institute for International Studies at Stanford University where her research focuses on Chinese military and security policy, Asia-Pacific security issues, war termination, and coercive diplomacy; a senior non-resident fellow at the American Enterprise Institute; an inaugural Wilson Center China fellow; and a fellow in the National Committee’s Public Intellectuals Program. She has published widely, including in Foreign Affairs, International Security, International Studies Review, Journal of Strategic Studies, The Washington Quarterly, The National Interest, Survival, and Asian Security. Her 2019 book, The Costs of Conversation: Obstacles to Peace Talks in Wartime, won the 2020 American Political Science Association International Security Section Best Book by an Untenured Faculty Member. 
Dr. Mastro holds a B.A. in East Asian studies from Stanford University and an M.A. and Ph.D. in politics from Princeton University.

Added from comments
:
Russia is discussed by the panelists. My guess is that if PRC launched a surprise invasion of TW they would just sit it out. The panelists go so far as to speculate that Russia might collaborate with PRC in the planning of an invasion, and could even provide some geopolitical distraction in support of it. I'm not sure I believe that -- the risk of losing surprise due to information leakage from the Russian side would be a big negative against coordination. 
There would be huge repercussions from nuking Japan (PRC actually has a no first use policy), but the emotional effect of, e.g., seeing a large PLAN ship sunk by a Japanese missile would be very strong. Remember, to PRC it looks like a (very much still disliked) foreign power intervening in an internal Chinese dispute. Sort of like Britain helping the confederacy during our civil war, but much worse. At the beginning of a TW invasion PRC might issue some kind of very strong ultimatum of non-interference to all parties (US, Japan, etc.) and then feel justified if the ultimatum is not obeyed. 
Please don't confuse descriptive analysis with normative analysis. It's important to understand how this looks from the other side, in order to predict their behavior. 
PRC faced down the US on the Korean peninsula when they had NO nuclear deterrent. (The historical record is clear that the US seriously considered using nukes against PRC over Korea and over TW in the past.) This would be a fight over (in their minds) actual Chinese territory, not Korea, and today they have a very credible MAD deterrent.
Re: item #3 above, I would like to see a detailed analysis of Taiwan's senior military leadership and their political leanings. I suspect that among them are many descendants of KMT military officers (like my father and grandfather), who largely still support the KMT political party and not the pro-independence DPP. These officers might lead a military coup in the event of a PRC invasion -- especially if it is a reaction to a DPP proclamation of independence, or other US-backed provocation.

 

This interview with Professor Alexander Huang of Tamkang University (Taiwan) Graduate Institute of International Affairs and Strategic Studies addresses the possibility of direct participation by the US and Japan in defense of Taiwan. In my opinion, Huang is realistic and well-calibrated.  


This is a clear explanation of the status quo, with opinion poll results:

Wednesday, August 04, 2021

Glenn Diesen on Geostrategy and Greater Eurasia

 
This is a good discussion of Eurasian geopolitics, Russia-China relations, decline of US empire, multipolarity, etc. 

Note Diesen, originally from Norway and now a professor there, was previously professor at the Higher School of Economics in Moscow. I find his writing on Russia and Eurasian geostrategy much more realistic than what is produced by most US or European academics and analysts. His latest book:
Europe as the Western Peninsula of Greater Eurasia Geoeconomic Regions in a Multipolar World 
GLENN DIESEN 
Will the increased economic connectivity across the Eurasian supercontinent transform Europe into the western peninsula of Greater Eurasia? The unipolar era entailed the US organising the two other major economic regions of the world, Europe and Asia, under US leadership. The rise of “the rest”, primarily Asia with China at the centre, has ended the unipolar era and even 500-years of Western dominance. China and Russia are leading efforts to integrate Europe and Asia into one large region. The Greater Eurasian region is constructed with three categories of economic connectivity – strategic industries built on new and disruptive technologies; physical connectivity with bimodal transportation corridors; and financial connectivity with new development banks, trading currencies and payments systems. China strives for geoeconomic leadership by replacing the US leadership position, while Russia endeavours to reposition itself from the dual periphery of Europe and Asia to the centre of a grand Eurasian geoeconomic constellation. Europe, positioned between the trans-Atlantic region and Greater Eurasia, has to adapt to the new international distribution of power to preserve its strategic autonomy.

Bonus: A good discussion of hypersonic missile technology and its strategic implications. See also LEO SAR, hypersonics, and the death of the naval surface ship. Effective ranges of hypersonic weapons that can be launched from land-based mobile TEL, submarine, small naval surface combatant, fighter jet, etc. are now in the thousands of kilometers. Combined with ubiquitous satellite imaging, we have a revolution in military affairs...

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