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Roger V.

 Discussion on answer by Roger V.: Wha…

Imported from a comment discussion on physics.stackexchange.co...
Roger V.
Jul 17 16:41
@JarekDuda "the system is dissipative and decohering in both temporal directions" - you might have missed the preceding comment on this: ""the system is dissipative and decohering in both temporal directions" - this means that mathematical equations and derivations used to describe physical phenomena are invariant in respect to time reversal. Physical time however moves in one direction."
Roger V.
Jul 17 16:41
@JarekDuda what we measure in quantum computers is the averages, as described above, even though between the measurements the evolution could be quantum, and the consequences of this quantum evolution are reflected in the final measurement. This is fundamental quantum mechanics. If you disagree, please provide a reference. See en.wikipedia.org/wiki/…
Roger V.
Jul 17 16:41
@JarekDuda " just waiting leads to the ground state: |0> - $|0\rangle, \langle 0|$ are not a measurable physical states, but state vectors in Hilbert space, which exist only in our imagination. Experimentally/physically we measure the occupation number in the ground state, which corresponds to the expectation value of operator $n_0=|0\rangle\langle 0|$: $\langle 0|n|0\rangle$.
Roger V.
Jul 17 16:41
@JarekDuda "the system is dissipative and decohering in both temporal directions" - this means that mathematical equations and derivations used to describe physical phenomena are invariant in respect to time reversal. Physical time however moves in one direction.
Roger V.
Jul 17 16:41
@JarekDuda Again, one has to distinguish math and physics. I think we have already agreed that on the mathematical level there is no difference between forward and backward evolution in time, i.e., it will be Lindbadian equation with minor adjustments. On the physical level - I don't see how one can have backward evolution given the same uncontrolled thermalization process (always forward in time.)
Roger V.
Jul 17 16:41
@JarekDuda "Evolving toward -t looks the same" - are you talking about matrix elements or about physical/laboratory observations? How do you reverse time in a lab?
Roger V.
Jul 17 16:41
@JarekDuda these are symmetric preparations for the q-bit, but the bath is always prepared in the same way?
Roger V.
Jul 17 16:41
@JarekDuda so before and after the unitary evolution we have the same non-unitary process with the same thermodynamic state preparation - so it evolves in the same direction. An even more core point is that irreversibility arises as a result of evolution of a system with infinite number of degrees of freedom, while the evolution of a system of a few degrees of freedom uncoupled from bath is reversible. The nature of the system and whether it is quantum changes little here - although some effects might be easier to observe in quantum setting.
Roger V.
Jul 17 16:41
@JarekDuda we can prepare/enforce initial state by waiting before - this is the same "thermodynamic/state preparation" as in the classical case. I could think of two systems of a very large number of q-bits (aka Heisenberg model) that we force to evolve unitary in two opposite ways $U(t)$ and $U(-t)$ - then provided finite precision or time averaging, we will get thermodynamic-like behavior ending in the same thermodynamic state - something like quantum version of Kac's ring. Evolving unitarily in opposite ways is just like like reversing direction of motion on the Kac's ring.
Roger V.
Jul 17 16:41
@JarekDuda Regarding the time reversal, to see more clearly, let's abundon quantum complications and look at a classical example. E.g., a ball in a bowl in Earth gravity field - it relaxes to the bottom of the bowl (state $x=0$). We can then "manipulate" the ball, e.g., by moving it to another position, and then let it roll back to the bottom of the bowl. In what sense do we have time reversal here?
Roger V.
Jul 17 16:41
@JarekDuda Another figure of language is that when we say that q-bit is prepared in a "state" $|0\rangle$ what we really mean is that the occupancy of state $0$ is 1: $\langle 0|n_0|0\rangle=1$. And even this statement is understood in a statistical sense - that after a million measurements in similar conditiosn we find the q-bit in this state.
Roger V.
Jul 17 16:41
@JarekDuda There is a difference between what we calculate and what we actually measure in experiments. Neither wave function, nor scattering matrix, nor Green's function are measurable quantities, while energy, state occupancy, scattering cross-section, and current are. So calling one matrix element "forward in time" and another "backward" is a matter of terminology, not of physics, because both enter the final result on equal footing.
Roger V.
Jul 17 16:41
@JarekDuda What you calculate in the end is an average of a hermitian operator. In scattering formalism that you refer to, we calculate in the end a scattering cross-section or something of the kind $|\langle \psi_f|U|\psi_i\rangle|^2=\langle \psi_i|U^\dagger|\psi_f\rangle \langle \psi_f|U|\psi_i\rangle$.
Roger V.
Jul 17 16:41
@JarekDuda You might be attributing some non-standard meaning to $|0\rangle$ and $\langle 0|$, which needs to be explained. From standard QM point of view, $\langle 0|$ is just a conjugate of a state vector $|0\rangle$ - neither of which is observable, since we observe only averages, not the wave function/state vectors. In an observable $|0\rangle$ and $\langle 0|$ would always appear in a combination.
Roger V.
Jul 17 16:41
@JarekDuda I am not sure that I grasp the key idea in the poster linked (there are many details related to the physical realization, which are probably not essential conceptually). Suppose I have a two-level system - I wait till it relaxes to the ground state, then I perform a unitary evolution, and then I wait again till it relaxes - in what sense time is reversed here? I probably miss some key detail...
 

 Discussion on answer by Roger V.: Do …

Imported from a comment discussion on academia.stackexchange.c...
Roger V.
Jul 12 03:46
@BryanKrause a good assumption would be that a person behind the question is an adult, capable of analyzing information and making their own decisions, who would not be swayed by a random opinion on SE. It is also healthy to assume that they may be just as old, experienced and accomplished as yourself.
Roger V.
Jul 12 03:46
@BryanKrause I just don't see what you try to prove by repeating banalities about copyright. Clearly, we are reusing stuff all the time - e.g., the English language - answering this Q. requires analysis of what is covered by copyright and what is not, which modifications are derivations, and which are new content. That so many in this thread refuse to even contemplate the issue is rather depressing. Are you under your real name here? - I would be curious to look zt the reviews and books that you have written.
Roger V.
Jul 12 03:46
@BryanKrause I think ganging up is appropriate in this circumstance - ganging up/bullying is never appropriate. You might want to review your university guidelines on this subject. Also, the paternalistic attitude towards the questionner is inappropriate and likely stems from incorrect assumptions about their background.
Roger V.
Jul 12 03:46
@BryanKrause moderator ganging up with a crowd to bully un unfortunate user. Noted. Btw, was the wow a sign of condescension?
Roger V.
Jul 12 03:46
@Dr.Snoopy FYI, the question in law even cites this one. You are acting bad faith.
Roger V.
Jul 12 03:46
@Buffy perhaps they appreciate that somebody actually looked into their problem, and helped them to learn something new - rather than reciting generic statements which added little to what the OP already knew.
Roger V.
Jul 12 03:46
@TimothyAWiseman please read the answer that you comment upon - it does not suggest publishing literal translation, but rather making changes and additions, to make the work sufficiently different under copyright law. Please also consult the linked thread in the Law community, where the limits of the copyright are discussed (does not apply to formulas, theorems, citation lists, and much of the content typically constituting a scientific review.)
Roger V.
Jul 12 03:46
@J-J-J these are generic links - none of these directly relates to the content of this answer, which points out the factual evidence that strikingly similar content is routinely published as reviews and books. And no one in this thread has provided any criteria of how much the work must differ to not violate a copyright (see an above example with QM textbook.)
Roger V.
Jul 12 03:46
@Sneftel well, the burden of proof is on you - give your definition and argue how it is inconsistent with what I stated (rather vaguely). Otherwise yours are empty words - this kind of condescending attitude may cut it in front of your humble undergraduates, but not with me.
Roger V.
Jul 12 03:46
@Sneftel Most of scientific work is derivative work - if I were to publish tomorrow my book on Quantum Mechanics, it would contain 99.9% of material already published in other books... yet, no one would dare to accuse me of plagiarism or infringing copyright (although of course this would not be considered "novel" as a research publication.) I could give plenty of examples... but I don't want to name well-known people. E.g., one could publish the results of one's research in Reviews of Modern Physics, then as one's PhD thesis, and finally as a stand-alone book.
Roger V.
Jul 12 03:46
@Buffy I explicitly mention the copyright: it prohibits from publishing the same thing, but not a similar one. And the criteria for similarity are not the same as for plagiarism.
 

 Discussion between Obie 2.0 and Not a…

Imported from a comment discussion on politics.stackexchange.c...
Roger V.
Jun 12 08:48
It's really a trivial test - apply whatever is said about Israel to another country in a similar situation, like the US and France and see whether it would be considered normal and appropriate. If not, you know how it is called.
Not all Oscars are Schindlers
Jun 12 08:47
You are misinterpreting what Sanchez said - criticizing Israel is one thing, namecalling is another. Would calling the US "murderous Yankees" be a "legitimate criticism" of its policies in Iraq?
Not all Oscars are Schindlers
Jun 12 08:41
I didn't tie anything. I reported a comment, which surprised me, because (as we discussed) a person with any sense of moral guilt would not make such a statement. It suggests high level of ignorance - hence the question. Even you here seem to insist that you do not apply word "genocide" to Israel.
Not all Oscars are Schindlers
Jun 12 08:38
I preferred to ask about facts - how do Spanish textbooks cover Spanish past. This way, it is not linked to the debate about Israel, and does not require comparing with Israel.
Not all Oscars are Schindlers
Jun 12 08:36
Then what stops them? - many of these people are highly visible or in power (like Pedro Sanchez). And on a lower level, many of them in this community were given opportunity to denounce Spanish crimes in the answers and comments to this question.
Not all Oscars are Schindlers
Jun 12 08:32
"It is, of course, entirely possible for someone to feel guilty (as you advocate) and also to admonish others for engaging in the behavior that they regret. It is perhaps even likely." - Indeed, but to do this, one has to first acknowledge one's own misdeeds. Without it, such criticism looks quite different.
Not all Oscars are Schindlers
Jun 12 08:31
Did Pedro Sanchez say anything about Sudan? Do you think our friends in Politics SE would be so excited, if the Q. mentioned Sudan rather than Israel? And if the Q. asked about a genocide in a third world, rather than about the ones committed by what is now a western nation?
Not all Oscars are Schindlers
Jun 12 08:29
When 50,000 people are killed - surely something has gone wrong. Same about half a million in Iraq or Afghanistan. It might be not illegal - it could be within the limits of the laws of war, but feeling guilty is more appropriate than adopting moral high ground and lecturing others
Not all Oscars are Schindlers
Jun 12 08:25
So you essentially keep insisting that Israel should be treated to a different standard. What about Sudan?
Not all Oscars are Schindlers
Jun 12 08:25
surely... as did Americans, Spanish, French, British, etc. Moreover, when talking about evens some 50+ years ago one cannot even claim the fog of war or lack of information - many archives are open by now.
Not all Oscars are Schindlers
Jun 12 08:22
"The Israeli government is doing little, if anything, wrong in Gaza, but if they did, all Israelis would be responsible, regardless of their beliefs and actions?"- straw man.
a) I don't know whether Israeli government is doing anything wrong in Gaza - I simply don't have the facts. Anyone who claims to have them is lying.
b) Regardless of that, Israel is being judged unfairly - an ongoing genocide in Gaza would merit some governmental/international action, but all the posturing by Americans, Spanish, French, etc. is hypocritical, and ultimately detrimental to the victims of the genocides co…
Not all Oscars are Schindlers
Jun 12 08:09
@Obie2.0 On the contrary, I think that German collective guilt is quite appropriate, it wasn't "just Nazis" or "just government" - those who did not participate in Holocaust either knew about it or deliberately ignored obvious signs. And I think the world would be a better place, if other nations recognized their misdeeds (not only when it is politically expedient.)
Not all Oscars are Schindlers
Jun 12 08:03
@Obie2.0 It is noble of you to acknowledge this. But there are still some elements missing: a) you do not call US actions in Iraq a genocide, and b) you dismiss it as Bush/Rice/Rove things - unlike Germany and Israel who are supposed to carry national responsibility. It is perhaps for the same reason that you ignore Afghanistan - since it cannot be squarely put on the Republicans.
Not all Oscars are Schindlers
Jun 12 07:55
@Obie2.0 Again, your claim is base don the elevated number of casualties (which is not known from independent sources). This argument is then valid, e.g., for the recent invasions of Iraq and Afghanistan, which resulted in ten-fold numbers of casualties.
Not all Oscars are Schindlers
Jun 12 07:45
@Obie2.0 The whole UN narrative is contradictory - on the one hand, they supposedly do not have access to Gaza... on the other, they have claim to have the facts. A casualty count independent from Hamas could be a good starter. Same could be said about the much valued "mainstream media". Also, Israel claims that UN agency was a party to the conflict - how can UN be an independent judge here?
Not all Oscars are Schindlers
Jun 12 07:45
@Obie2.0 I think you should be more clear on whether you uphold international law or the sympathies "mainstream people" - these may disagree quite a bit. Also, which "mainstream people" exactly? - those in the ME or westerners? And to what extent the opinion of the "mainstream people" is affected by religious and political leaders, and the media? If Palestinian refugees in 1948 were not used as a bargaining chip against western colonialism in the form of Israel, perhaps history would be different.
Not all Oscars are Schindlers
Jun 12 07:45
@ItalianPhilosopher your very first comment claims that the questions should not be asked about countries that criticized Israel.
Not all Oscars are Schindlers
Jun 12 07:45
@Obie2.0 FYI, separate Palestinian communities in nearby countries ("refugee camps") has existed since 1948. Nobody calls them "apartheid". E.g., Palestinians born in Lebanon, even in 2nd or 3rd generation do not have rights of Lebanese citizens or even foreign workers - they cannot be legally employed, own a property, etc. outside of the camps. Conversely,
Not all Oscars are Schindlers
Jun 12 07:45
@ItalianPhilosopher nowadays, when one talks about a genocide, one naturally thinks about Israel - so no wonder that it comes up in questions about genocides. The rest is just a product of sick imagination/brain-washing.
Not all Oscars are Schindlers
Jun 12 07:45
@ItalianPhilosopher again, your claim is that just because Spain criticizes Israel, it should be beyond criticism and no questions should be asked. Again, it is your who make it all about Israel. It could have been a calm discussion about Spain, if you and others were not so obsessed.
Not all Oscars are Schindlers
Jun 12 07:45
@Obie2.0 is this your opinion personal or a legal judgement? Most wars fit "killing members of the group" - even abstracts ones like "war on terror" (because all the killed are members of the "terrorist" group.)
Not all Oscars are Schindlers
Jun 12 07:45
@sfxedit FYI, "whataboutism" is only a fallacy in a formal debate, which assumes existence of an impartial judge. Here the accusers act as judges - quite contrary to the western notion of justice. There are also expressions like projecting colonial guilt and The Germans Will Never Forgive the Jews for Auschwitz.
Not all Oscars are Schindlers
Jun 12 07:45
@Obie2.0 As I pointed above, I don't see why the situation in Gaza should preclude discussion of crimes committed by other nations. Those however raise the question if impartiality, collective guilt, and possibly even colonialist attitudes (aka, western people are more moral than middle-eastern savages.)
Not all Oscars are Schindlers
Jun 12 07:45
@Obie2.0 well, technically nothing that took place more than a hundred years ago qualifies as genocide or war crime or even an atrocity under international law, since this did not exist in its current form. Neither the actions in Gaza so far, btw.