Do superpositions violate conventional logic (philosophy)?

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  • #26
jambaugh
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amblerise,

The article's phrasing of " ... simultaneously being 'a' and 'not a'..." is very bad poetic license attempting to describe quantum superposition in classical vernacular.

It is important understand that the term superposition is first applied, not to the quantum system, but rather to the measuring devices. Consider photon polarization for a moment. You can have a Polaroid film in front of a photon detector so that it will only click for vertically polarized photons and never click for horizontally polarized photons. By "vert. photons" etc we mean photons which have already passed through a vertical polarizer and likewise with all other "states". Note that we cannot know anything about the photons except in how they behave with respect to measuring devices. But what we see is that all photons will either pass through a vertical polarizer or through a horizontal polarizer. So it would seem that photons only come in two states, horizontal and vertical.

Then we look at them all again 45deg turned and notice that all photons are either left-oblique or right oblique. The oblique polarizers, as measuring devices, are superpositions of the vert/horiz. polarizers. A photon measured with vertical polarization will sometimes pass through the left-oblique and sometime through the right oblique. (Note we can non-destructively determine which with a birefringent crystal such as calcite.)

This lead us to abandon (at first) thinking in terms of the photons as having an objective state independent of our choice of measurement. We simply identify photons as phenomena (not objects) which behave in a probabilistically predictable way.

That plus some other points is the Copenhagen Interpretation. Now other interpretations try to build a more involved "reality" of the photon below what is observable, e.g. many worlds and pilot waves.

To avoid confusion about the logic of quantum mechanics it is important to stick to only statements about what has been or will be observed and forget about statements about the state of the system excepting as they translate to what has been/will be observed.
 
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I'm left wondering how the concept of superposition is reconciled with conventional notions of logic in philosophy. Also, does the standard notion of logic collapse if there is no clear reconciliation (i.e. are we then forced to admit to the fallibility of conventional logic)?


superpositions can be break if nature is nonlinear, nonlinearity break the linearity of the superposition.


.
 
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No wonder physicists need an infinite number of worlds to explain ours(or rather explain it away).

I think that 'many worlds' is a relatively funny science fiction idea.

I do not understand how it can be taken seriously.
 
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jambaugh
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I think that 'many worlds' is a relatively funny science fiction idea.

I do not understand how it can be taken seriously.

Yea, the one thing that grates on my nerves when I watch SciFi programs is when the "science expert" inevitably says... "yes, quantum mechanics predicts an infinity of parallel universes...". I go AHHHHRRRRRGGGG!!!! NO IT DOESN'T and throw pillows at the TV. Too many people grow up hearing this because it makes the best premise for the "magic" in these fantasies.

The writers could at least change it to "... one interpretation of QM predicts...".

In Everett's defense, there is some virtue in his "relative state" approach and I want to spend more time looking at his original thesis rather than the MW into which it evolved.
 
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To avoid confusion about the logic of quantum mechanics it is important to stick to only statements about what has been or will be observed and forget about statements about the state of the system excepting as they translate to what has been/will be observed.
A superposition is a transition phase, with a probability of 50 percent, which results in either a positive or a negative observation. It's not really an end state like the probability of a tossed coin sitting on its edge but more like an intermediate phase between one outcome and another.

If you look any closer at the transition phase it implies an initial state, a transition phase, and an observed state with a range of change from its initial state of 0 or 1 (i.e. True, transition, True and False, transition, False have no state change while True, transition, False and False, transition, True have a total state change).

Could a quantum superposition be considered a start state?
 
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Yea, the one thing that grates on my nerves when I watch SciFi programs is when the "science expert" inevitably says... "yes, quantum mechanics predicts an infinity of parallel universes...". I go AHHHHRRRRRGGGG!!!! NO IT DOESN'T and throw pillows at the TV. Too many people grow up hearing this because it makes the best premise for the "magic" in these fantasies.

The following is a good example of ambiguity :wink: "while some people think that black holes are portals to other universes, in reality they are just exceedingly dense pricks".
 
  • #32
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I recently read a research summary about using magnetic fields to briefly maintain quantum states in relation to quantum computing. The article makes reference to "a" simultaneously being "a" and "not 'a'".
This is, imo, just a bad way of talking about the formalism.

I'm left wondering how the concept of superposition is reconciled with conventional notions of logic in philosophy. Also, does the standard notion of logic collapse if there is no clear reconciliation (i.e. are we then forced to admit to the fallibility of conventional logic)?
Conventional logic still holds. Just don't make the mistake of thinking of mathematical quantum states or superpositions as real states, ie., of descriptions of what's actually happening in the underlying reality.

My only thought thus far is found in browsing the Copenhagen interpretation (which I admittedly don't clearly understand the mechanics of). The Copenhagen interpretation inspires the thought that particles have at least two states and can therefore be two things simultaneously.
Then you've just misunderstood the essence of the Copenhagen Interpretation.

The quantum theory is a probability calculus. Quantum superpositions are expressions of experimental possibilities. There's no implication that "the particle is in two places simultaneously", or that "the particle exists and doesn't exist simultaneously", or whatever.
 
  • #33
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Conventional logic still holds. Just don't make the mistake of thinking of mathematical quantum states or superpositions as real states, ie., of descriptions of what's actually happening in the underlying reality.


...because your obviously classical mindset can explain the quantum? You know what they say - "If i haven't seen it, it doesn't exist!". If it doesn't behave according to my predjucies it's not real(even though the registered pattern on the screen of the double slit experiment is obviously a result of a something passing through both slits simultaneously). As far as i know, for very good reasons, the whole 'particle' way of thinking was found to be a misconception more than half a century ago.



The quantum theory is a probability calculus. Quantum superpositions are expressions of experimental possibilities. There's no implication that "the particle is in two places simultaneously", or that "the particle exists and doesn't exist simultaneously", or whatever.



That's your philosophy and it's acceptable and it's right where it belongs. But if you come to really think about it, the classical mindset is not a gift from god, it's likely a misconception(as evidenced by the philosophical implications of SR too)

PS. If superpositional states aren't real, what is this underlying reality you speak of? It sure can't be real as far as a classical mindset can grasp it. An equation?
 
  • #34
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...because your obviously classical mindset can explain the quantum? You know what they say - "If i haven't seen it, it doesn't exist!". If it doesn't behave according to my predjucies it's not real(even though the registered pattern on the screen of the double slit experiment is obviously a result of a something passing through both slits simultaneously). As far as i know, for very good reasons, the whole 'particle' way of thinking was found to be a misconception more than half a century ago.
What I'm saying is that quantum superpositions don't violate conventional logic in the sense that it was conventional logic that led to their formulation, and that they also don't (in and of themselves wrt their form and content) violate conventional logic as long as one takes them as what they are (expressions of relationships between and among instrumental possibilities) as part of a mathematical formalism designed to generate statistical probabilities wrt instrumental behavior, and doesn't attribute any deeper significance to them.

That's your philosophy and it's acceptable and it's right where it belongs. But if you come to really think about it, the classical mindset is not a gift from god, it's likely a misconception (as evidenced by the philosophical implications of SR too).
Our mindset is necessitated and constrained by our sensory capabilities. So is our capacity for explanation, understanding, and unambiguous communication.

But given those limitations, it doesn't necessarily follow that the deep reality must be essentially different from the reality of our sensory experience. That is, I like the assumption that there are fundamental dynamical laws governing all physical realms, and that apparently scale and realm specific organizing principles have emerged from those fundamental laws.

What misconceptions do you think are "evidenced by the philosophical implications of SR"?

If superpositional states aren't real, what is this underlying reality you speak of?
Nobody knows what the underlying reality is. Nobody can know. Which is precisely why quantum superpositions shouldn't be taken as referring to the underlying reality.
 
  • #35
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What I'm saying is that quantum superpositions don't violate conventional logic in the sense that it was conventional logic that led to their formulation, and that they also don't (in and of themselves wrt their form and content) violate conventional logic as long as one takes them as what they are (expressions of relationships between and among instrumental possibilities) as part of a mathematical formalism designed to generate statistical probabilities wrt instrumental behavior, and doesn't attribute any deeper significance to them.



It's not known to me how the interference pattern on the screen of the double slit experiment can arise out of a mathematical formalism. If your theory doesn't match reality, you change the theory, not the reality.



Our mindset is necessitated and constrained by our sensory capabilities. So is our capacity for explanation, understanding, and unambiguous communication.

But given those limitations, it doesn't necessarily follow that the deep reality must be essentially different from the reality of our sensory experience. That is, I like the assumption that there are fundamental dynamical laws governing all physical realms, and that apparently scale and realm specific organizing principles have emerged from those fundamental laws.



Sure, but i was objecting to using the classical mindset and its baggage for defining quantum realism, which by all means seems to best described as an interaction of fields(with real and unreal components at the same time, as evidenced by a multitude of experiemnts). The classical mindset is a deadend(this is not an opinion, we need to move on, though admittedly i will be the last person to usher the new one).

What misconceptions do you think are "evidenced by the philosophical implications of SR"?


In case you have forgotten(I doubt that), SR changed drastically our understanding of the structure of the universe with its previously fixed properties(mass, length, time, speed, energy, simultaneity, etc.). This is a side point and a quick google search will bring up quite a number of relevant points on how the classical mindset is a misconception for explaining reality(as supported by SR).


Nobody knows what the underlying reality is. Nobody can know. Which is precisely why quantum superpositions shouldn't be taken as referring to the underlying reality.


Nobody knows what this reality is and at this point, it appears that nobody can know. You probably won't like an argument based on it alone that argues that it's not real. Also, i don't see where anyone referred the existence of superpositions to a supposed underlying reality(i thought they referred to our reality - they can be observed as interference patterns).

The bottom line, imo(i think even the staunchest of realists would agree), is that we are far far away from the idea of a classical universe with definite properties that takes up a definite volume and dimensions in time. You probably don't like the direction physics appears to be going, but if 'matter' is a something that exists out there, we'll need a something akin to a probabalistic field 'universe' to explain it in a consistent manner. Or it could be that physics cannot say anything meaningful about reality(the universe, heh) and its ontology and whatever seems to be happening and existing will forever remain unexplained in a self-consistent manner, as some scientists assert(it never was, anyway).
 
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It's not known to me how the interference pattern on the screen of the double slit experiment can arise out of a mathematical formalism. If your theory doesn't match reality, you change the theory, not the reality.

Sure, but i was objecting to using the classical mindset and its baggage for defining quantum realism, which by all means seems to best described as an interaction of fields(with real and unreal components at the same time, as evidenced by a multitude of experiemnts). The classical mindset is a deadend(this is not an opinion, we need to move on, though admittedly i will be the last person to usher the new one).

In case you have forgotten(I doubt that), SR changed drastically our understanding of the structure of the universe with its previously fixed properties(mass, length, time, speed, energy, simultaneity, etc.). This is a side point and a quick google search will bring up quite a number of relevant points on how the classical mindset is a misconception for explaining reality(as supported by SR).

Nobody knows what this reality is and at this point, it appears that nobody can know. You probably won't like an argument based on it alone that argues that it's not real. Also, i don't see where anyone referred the existence of superpositions to a supposed underlying reality(i thought they referred to our reality - they can be observed as interference patterns).

The bottom line, imo(i think even the staunchest of realists would agree), is that we are far far away from the idea of a classical universe with definite properties that takes up a definite volume and dimensions in time. You probably don't like the direction physics appears to be going, but if 'matter' is a something that exists out there, we'll need a something akin to a probabalistic field 'universe' to explain it in a consistent manner. Or it could be that physics cannot say anything meaningful about reality(the universe, heh) and its ontology and whatever seems to be happening and existing will forever remain unexplained in a self-consistent manner, as some scientists assert(it never was, anyway).
Your points are taken, and I think that some might be great starters for new threads. Wrt the OP, I think that jambaugh gave the best answer. So, I would defer to him wrt any future elaborations on the OP question(s)/considerations. I've expressed my opinion wrt the OP in prior posts.
 
  • #37
jambaugh
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It's not known to me how the interference pattern on the screen of the double slit experiment can arise out of a mathematical formalism. If your theory doesn't match reality, you change the theory, not the reality.

More to the point, it's when theory doesn't match observation that we chance the theory. Note that implicit in your phrase is the assertion that one can seem to "change reality" which goes to show any assertion of "reality" is itself a theory (or more properly a model). Below the level of "realities" is the level of phenomena.

It is exactly the failure of reality models to match observations (e.g. of Bell inequality violating EPR/Aspect type experiments) that leads us to change that component of the theory and recognize that it is observed phenomena and not reality pictures which is fundamental in the epistemological domain within which science operates.

This leaves us doing science using CI for quantum systems and then we are free to speculate in the philosophical domain over beers at the local pub with various "quantum realities" if we like... provided we understand that we are "off the clock" and outside the domain of physics.

It is critical though to understand why this is "off the clock". It is tautological that you can't empirically verify beyond the empirically verifiable... i.e. you can't speak scientifically about ontological reality beyond the observable be it classical reality or some exotic new creation of the mind.
 
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It is critical though to understand why this is "off the clock". It is tautological that you can't empirically verify beyond the empirically verifiable... i.e. you can't speak scientifically about ontological reality beyond the observable be it classical reality or some exotic new creation of the mind.



Even if we accept what you seem to imply - that we can only hope to describe reality, and not understand it scientifically, what does it mean to you that the constituents of reality as we know them today(elementary particles) have properties(observables which are empirically verifiable as you say) without a corresponding structure? This is not just a question for philosophy and talks at the bar, but for science. If the bulding blocks don't have a structure, then the world either operates on magic or is not real. Alternatively, it could be illogical which is a real option as well and would be an epistemic limit, but all 3 are surely very unfavorable to science as we have been accustomed to apprehending it(i've seen quite a lot of physicists here on PF and elsewhere who refuse to even think about such questions as if they were unscientific - out of fear i suppose).
 
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  • #39
jambaugh
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Even if we accept what you seem to imply - that we can only hope to describe reality, and not understand it scientifically, what does it mean to you that the constituents of reality as we know them today(elementary particles) have properties(observables which are empirically verifiable as you say) without a corresponding structure?
What do you mean by "a corresponding structure"? There is the structure of their observables i.e. spectrum and fixed charges, and the transformation properties of their observables a la gauge model but all of this is phenomenological and I don't think that's what you mean.

This is not just a question for philosophy and talks at the bar, but for science. If the bulding blocks don't have a structure, then the world either operates on magic or is not real.
Yes, exactly, and it's not magic. But I distinguish "real" from "actual". The actual world (world of actions) exists apart from the observer but the description of the world in terms of a sequence of states of reality is inappropriate. Assertions of the existence of a "world of reality" as such is a assertion outside the bounds of science. Again remember that when seeking "what is most fundamental" there is a question of context.

If you presuppose an ontological context then you seek the "atoms" the underlying building blocks, the structure of a reality.

If you rather are in the context of epistemological empiricism a.k.a. science then what is most fundamental is the act of observation... most precisely the boolean observable such as the "click" or a "particle" detector. From this fundamental building block you build up the logic of correlated experimental acts and test assertions developing a theory of how phenomena behave. You can likewise make probabilistic assertions about aggregate phenomena and this is what we have in Quantum Physics.

Alternatively, it could be illogical which is a real option as well and would be an epistemic limit, but all 3 are surely very unfavorable to science as we have been accustomed to apprehending it(i've seen quite a lot of physicists here on PF and elsewhere who refuse to even think about such questions as if they were unscientific - out of fear i suppose).

I don't see it as "refusing to even think about such questions" but rather properly classifying the questions as scientific, meta-scientific, and exo-scientific.

Remember the power of science is that in a debate there is an ultimate judge as to who is right and who is wrong... go out and observe the facts. As we push the frontier, of course this act of judgment isn't always simple or easy. But is enforces a discipline on the format of the questions. That discipline rejects questions which cannot, even in principle, be so judged as unscientific; e.g. questions like "whether God prefers vanilla ice-cream to chocolate (or more typically ethnic group A to ethnic group B)".

My point is that "questions about reality beyond the observable" are exactly like questions of divine flavor preferences.
(This is, by the way, a meta-scientifc assertion about the exo-scientific status of the specific questions.)
 
  • #40
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What do you mean by "a corresponding structure"?


A corresponding causal structure would typically possess spatially extended and measureable dimensions plus internal structure that determines the behavior of the most basic constituents of reality. Such structure cannot be found




There is the structure of their observables i.e. spectrum and fixed charges, and the transformation properties of their observables a la gauge model but all of this is phenomenological and I don't think that's what you mean.


Yes, i wasn't referring to observables(and their phenomenogy) but to the lack of causal structure that determines them(the registered outcomes).


Yes, exactly, and it's not magic. But I distinguish "real" from "actual". The actual world (world of actions) exists apart from the observer but the description of the world in terms of a sequence of states of reality is inappropriate. Assertions of the existence of a "world of reality" as such is a assertion outside the bounds of science. Again remember that when seeking "what is most fundamental" there is a question of context.

If you presuppose an ontological context then you seek the "atoms" the underlying building blocks, the structure of a reality.

If you rather are in the context of epistemological empiricism a.k.a. science then what is most fundamental is the act of observation... most precisely the boolean observable such as the "click" or a "particle" detector. From this fundamental building block you build up the logic of correlated experimental acts and test assertions developing a theory of how phenomena behave. You can likewise make probabilistic assertions about aggregate phenomena and this is what we have in Quantum Physics.



I don't see it as "refusing to even think about such questions" but rather properly classifying the questions as scientific, meta-scientific, and exo-scientific.

Remember the power of science is that in a debate there is an ultimate judge as to who is right and who is wrong... go out and observe the facts. As we push the frontier, of course this act of judgment isn't always simple or easy. But is enforces a discipline on the format of the questions. That discipline rejects questions which cannot, even in principle, be so judged as unscientific; e.g. questions like "whether God prefers vanilla ice-cream to chocolate (or more typically ethnic group A to ethnic group B)".

My point is that "questions about reality beyond the observable" are exactly like questions of divine flavor preferences.
(This is, by the way, a meta-scientifc assertion about the exo-scientific status of the specific questions.)



Agreed, but my point stays. If science cannot provide a mechanism(or structure) by which a quantum outcome is selected and actualized(and hence is macroscopically observed as an observable - what we normally refer to as 'reality', 'matter'...), then scientifically, the world operates on magic, and by this i strictly refer to the classical world of observations. Our observations are grounded in fundamental probabilities(fuzziness) and not in a preexisting, mechanistic, spatially extended structures. What exists is anybody's guess(you scientists would call that 'quantum system' to remain ever more vague) though what is observed is generally agreed upon among the obeservers.
 
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  • #41
jambaugh
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A corresponding causal structure would typically possess spatially extended and measureable dimensions plus internal structure that determines the behavior of the most basic constituents of reality. Such structure cannot be found
To observe causal structure you must observe. The causal correlations between experimental actions is well represented in the quantum formal language by the metric of the Hilbert space.

The action: [itex] \langle \psi |[/itex] ("prepare a system in mode [itex]\psi[/itex]") causes the action [itex] | \psi \rangle[/itex] ("detect a system in mode [itex]\psi[/itex]"), 100% of the time.

Other non-parallel sequences are less certain and more involved actions can be decomposes into these basic ones.
Yes, i wasn't referring to observables(and their phenomenogy) but to the lack of causal structure that determines them(the registered outcomes).

[...]Agreed, but my point stays. If science cannot provide a mechanism(or structure) by which a quantum outcome is selected and actualized(and hence is macroscopically observed as an observable - what we normally refer to as 'reality', 'matter'...), then scientifically, the world operates on magic, and by this i strictly refer to the classical world of observations. Our observations are grounded in fundamental probabilities(fuzziness) and not in a preexisting, mechanistic, spatially extended structures. What exists is anybody's guess(you scientists would call that 'quantum system' to remain ever more vague) though what is observed is generally agreed upon among the obeservers.

Firstly you are invoking the false alternative "either ____ or 'magic' "... unless you have a rather broad definition of 'magic'.

Secondly; Are you talking about the measurement "problem" here?

Note that "preexiting, mechanistic, spatially extended structures." sounds an awful lot like a reality model. What you are seeking results in an infinite regress; "elephants all the way down". Whatever structural components you might hypothesize must then be phenomenologically explained through observation of behavior (if we seek to remain in science) and you would then insist again on the causal substructure of THAT.

It is similar to the question of abiogenesis within the theory of evolution since evolution only addresses how existing life adapts, not its formation from inanimate material. You can't explain abiogenesis within evolution but must step outside (physics, chemistry, and thermodynamics).

Here the issue is more profound and more significant. We can easily explain the emergence of classical reality within a realm of quantum phenomena but we cannot, within the scope of science as a phenomenological discipline, "explain" quantum phenomena with a "deeper ontological model". But this isn't a failing or a problem. It is rather the recognition of the nature of knowledge and the mystical status of ontology.

This is why I invoke the point about contexts of "what is fundamental". In the end we must leave the domain of science or be resigned to stop at the phenomenological description. "$h!# Happens!" and at the lowest level we only describe the probabilistic rules of how and when it happens, not the why based on an underlying reality.

The student of quantum physics must at some point understand this just as the child must eventually come to understand that there ain't no Santa Claus nor Tooth Fairy. To the child these realizations are disappointments. But to the adult it is a relief that the world doesn't have such screwy and ad hoc rules as to allow fat elves to fly through the air on sleds pulled by magic reindeer.

Similarly accepting phenomenological fundamentalism allows us to (in principle) dispense with medieval arguments about how many angels can dance on the head of a pin. On a more practical footing, if the point ever filters up through the academic world, I would hope it would allow us to dispense with attempts to construct a TOE out of strings and branes and "quantized space-time" and put more resources into a more direct attack of the quantum gravity problem.
 
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The action: [itex] \langle \psi |[/itex] ("prepare a system in mode [itex]\psi[/itex]") causes the action [itex] | \psi \rangle[/itex] ("detect a system in mode [itex]\psi[/itex]"), 100% of the time.



In some circles(e.g. Tegmark and co.) this could easily pass as a structure on which reality is built. I am hesitant to call it anything more than a representation though.






This is why I invoke the point about contexts of "what is fundamental". In the end we must leave the domain of science or be resigned to stop at the phenomenological description. "$h!# Happens!" and at the lowest level we only describe the probabilistic rules of how and when it happens, not the why based on an underlying reality.




That things happen like that at the lowest level(potentials and actualization) and still there is something to call a perfectly causal and self-consistent classical world(with billions of years of history!), is a miracle in its own right(it doesn't matter to a philosopher looking for a deeper understanding that you can decribe probabilistically what might get actualized). But i agree, this is leaving science(it's allowed here i think, as long as its grounded in a mainstream hypothesis/interpretation - i've seen much worse offenders)
 
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  • #43
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In some circles(e.g. Tegmark and co.) this could easily pass as a structure on which reality is built. I am hesitant to call it anything more than a representation though.
agreed.
That things happen like that at the lowest level(potentials and actualization) and still there is something to call a perfectly causal and self-consistent classical world, is a miracle in its own right(it doesn't matter to a philosopher looking for a deeper understanding that you can decribe probabilistically what might get actualized). But i agree, this is leaving science(it's allowed here i think as long as its grounded in a mainstream hypothesis/interpretation - i've seen much worse offenders)
ditto. Nothing wrong with leaving the country as long as you do it knowingly and do not pretend to rely on the same rules. In this domain we arbitrate disputes differently, Occam's razor, and individual esthetics can come into play, and ultimately to my mind the potential of such speculation to build scaffolding for the construction of new physics. (Though I personally don't believe much more can be gleaned by pondering substructure in QM... rather we should eliminate the dependence on substructure e.g. de-objectify space-time which equates to moving away from theories based on fiber-bundles such as QFT and String Theory. But thinking that way is very hard; just as the transition from classical to quantum is conceptually hard. )
 
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This mind set doesn't provide a very solid philosophical foundation for quantum computing.
 

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