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"Isn't this article about the tech? Why are we suddenly having an extremely off-the-cuff discussion on whether HFT is "good or bad"?" Since when is tech automa

"Isn't this article about the tech? Why are we suddenly having an extremely off-the-cuff discussion on whether HFT is "good or bad"?" Since when is tech automatically amoral? I mean sure, the technology itself doesn't care, but that doesn't mean we shouldn't. You can discuss both simultaneously. Regarding the "laws of physics." Quantum mechanics does open up several possibilities for violating the speed of causality.[1] There is nothing that says any of the laws are fundamental truths, they are simply the way things always work, so far as we know. It's quite likely we will find exceptions. 1: http://www.bmeacham.com/whatswhat/Quantum.html#2.3.Causal%20Discontinuity%7Coutline http://www.bmeacham.com/whatswhat/Quantum.html#2.3.Causal%20...

drauh 10y ago
QM does not open up any avenues for violating causality. bmeacham.com is crackpot based on my reading the first 2 paragraphs. Usually, misunderstandings about causality come from a naive reading of the terms "advanced" and "retarded" solutions to wave equations, which also show up in classical electromagnetic theory. https://en.wikipedia.org/wiki/Green's_function_(many-body_theory) https://en.wikipedia.org/wiki/Green's_function_(many-body_th...
- Practicality 10y ago
  Ok. Here is a better source for you: https://arxiv.org/abs/1401.0167 https://arxiv.org/abs/1401.0167 bmeacham was just the first search result that was trying to explain the general concept I was referring to, so I don't have to write an article in the comments :)
  - Practicality 10y ago
    Cornell seems to like putting out phd theses on this subject: https://arxiv.org/abs/1607.07871 https://arxiv.org/abs/1607.07871 https://arxiv.org/abs/1608.01528 https://arxiv.org/abs/1608.01528 https://arxiv.org/abs/1607.00381 https://arxiv.org/abs/1607.00381 https://arxiv.org/abs/1605.06022 https://arxiv.org/abs/1605.06022 Seems like Cornell is wasting a lot of time researching something that you've already determined is impossible.
    - jessriedel 10y ago
      Everything you're linking too is either highly speculative (e.g, hypothetically taking place yoctoseconds after the big bang, and completely unconfirmed) or is addressing some subtle interpretative senses of causality which are very distinct from the normal sense (such as the paper by Leifer and Pusey, who worked/work down the hall from me).
  - jessriedel 10y ago
    That paper is discussing nonlinear quantum mechanics, models of which are almost always internally inconsistent. More importantly, it's just speculation; the kind of quantum mechanics that has been confirmed in the lab is linear. It's well known that quantum mechanics does not violate causality (when defined appropriately in terms of actual observations).
    - Practicality 10y ago
      But my whole point was speculating that it's possible, not that it's proven to be true. So of course I am citing speculative sources, this is speculation... :\
      - jessriedel 10y ago
        Although it may sound like it, I don't believe it's splitting hairs to draw an important distinction between (a) speculation that might be observable in our lifetime, or might have relevance to stock trading, and (b) speculation that has fundamental inconsistencies with deep principles on which the entire known body of physics knowledge is based, and which would revolutionize our understanding of the universe and the nature of reality if true. Here's another way to say it: time travel is strictly less crazy than acausality. Sorry, not trying to be a buzzkill :)
        Practicality 10y ago
        Not a problem. I prefer learning to being right :)
AnimalMuppet 10y ago
> It's quite likely we will find exceptions. That's obviously some definition of "likely" other than the one I am familiar with.
- Practicality 10y ago
  One that refers to an larger time frame than you are probably thinking of. See several of Newton's laws of physics having exceptions the scientific community was not aware of for a long time. I am not saying this going to happen in any of our lifetimes. But given a large enough time-frame, I am pretty sure most of our current understanding will turn out to be terribly inaccurate at an absolute level (although a good approximation based on what we currently understand)
  - AnimalMuppet 10y ago
    For any time frame that spans the human race, I consider it highly unlikely that we will find any exceptions to the speed of causality. Yes, I recognize that the possibility exists. Yes, I recognize that our understanding of the laws of physics grows over time. "Quite likely"? Still no.
    - Practicality 10y ago
      I didn't say it was likely we would find something violate causality, I said it was likely we would find exceptions to some of the laws of physics. I know those sentences were next to each other, so I could have separated the flow of my thoughts a little better. I thought causality was something not-as-well-proven as it currently is (because the history of QM always explains lots of interpretations where causality is broken). However, I stand corrected on that point :)

drauh 10y ago

QM does not open up any avenues for violating causality. bmeacham.com is crackpot based on my reading the first 2 paragraphs. Usually, misunderstandings about causality come from a naive reading of the terms "advanced" and "retarded" solutions to wave equations, which also show up in classical electromagnetic theory. https://en.wikipedia.org/wiki/Green's_function_(many-body_theory) https://en.wikipedia.org/wiki/Green's_function_(many-body_th...

Practicality 10y ago
Ok. Here is a better source for you: https://arxiv.org/abs/1401.0167 https://arxiv.org/abs/1401.0167 bmeacham was just the first search result that was trying to explain the general concept I was referring to, so I don't have to write an article in the comments :)
- Practicality 10y ago
  Cornell seems to like putting out phd theses on this subject: https://arxiv.org/abs/1607.07871 https://arxiv.org/abs/1607.07871 https://arxiv.org/abs/1608.01528 https://arxiv.org/abs/1608.01528 https://arxiv.org/abs/1607.00381 https://arxiv.org/abs/1607.00381 https://arxiv.org/abs/1605.06022 https://arxiv.org/abs/1605.06022 Seems like Cornell is wasting a lot of time researching something that you've already determined is impossible.
  - jessriedel 10y ago
    Everything you're linking too is either highly speculative (e.g, hypothetically taking place yoctoseconds after the big bang, and completely unconfirmed) or is addressing some subtle interpretative senses of causality which are very distinct from the normal sense (such as the paper by Leifer and Pusey, who worked/work down the hall from me).
- jessriedel 10y ago
  That paper is discussing nonlinear quantum mechanics, models of which are almost always internally inconsistent. More importantly, it's just speculation; the kind of quantum mechanics that has been confirmed in the lab is linear. It's well known that quantum mechanics does not violate causality (when defined appropriately in terms of actual observations).
  - Practicality 10y ago
    But my whole point was speculating that it's possible, not that it's proven to be true. So of course I am citing speculative sources, this is speculation... :\
    - jessriedel 10y ago
      Although it may sound like it, I don't believe it's splitting hairs to draw an important distinction between (a) speculation that might be observable in our lifetime, or might have relevance to stock trading, and (b) speculation that has fundamental inconsistencies with deep principles on which the entire known body of physics knowledge is based, and which would revolutionize our understanding of the universe and the nature of reality if true. Here's another way to say it: time travel is strictly less crazy than acausality. Sorry, not trying to be a buzzkill :)
      - Practicality 10y ago
        Not a problem. I prefer learning to being right :)

AnimalMuppet 10y ago

> It's quite likely we will find exceptions. That's obviously some definition of "likely" other than the one I am familiar with.

Practicality 10y ago
One that refers to an larger time frame than you are probably thinking of. See several of Newton's laws of physics having exceptions the scientific community was not aware of for a long time. I am not saying this going to happen in any of our lifetimes. But given a large enough time-frame, I am pretty sure most of our current understanding will turn out to be terribly inaccurate at an absolute level (although a good approximation based on what we currently understand)
- AnimalMuppet 10y ago
  For any time frame that spans the human race, I consider it highly unlikely that we will find any exceptions to the speed of causality. Yes, I recognize that the possibility exists. Yes, I recognize that our understanding of the laws of physics grows over time. "Quite likely"? Still no.
  - Practicality 10y ago
    I didn't say it was likely we would find something violate causality, I said it was likely we would find exceptions to some of the laws of physics. I know those sentences were next to each other, so I could have separated the flow of my thoughts a little better. I thought causality was something not-as-well-proven as it currently is (because the history of QM always explains lots of interpretations where causality is broken). However, I stand corrected on that point :)