fanieh said:
Thanks. Supposed the dark matter sector has many kinds of density and particles... in fact I read in the Scientific American how the dark matter can form dark chemistry.
Please provide a citation so I know what you are talking about.
Then supposed the mass of this special dark matter is not the same as the one you depicted in the web you gave where it is nanograms but much lighter than electron.
So what? Let's suppose that dark matter comes in different particles with different masses... we are now in the realms of pure speculation unless you can provide a citation. Mine was really recent. I can find stuff on dark Matter that says pretty much anything I want if I don't care about being up to date or accurate.
Then this dark matter baseball with deBroglie wavelength greater than say electron is a quantum object... a macroscopic quantum object.
What dark matter baseball? Why is it important that the baseball be made of dark matter? Why is it important that it is a baseball?
What do you mean by "quantum object"? What do you mean by "macroscopic object"? How do you determine size?
I have repeatedly asked you to speak clearly and you continue to refuse to do so.
Until you do you will get nowhere and nobody can help you.
Shouldn't it be in pure state theoretically assuming it has no interaction with any of the known forces preventing decoherence except the force of gravity? Can the quantum baseball be decohered by gravity.. but it looks like it can't.. why can't it?
You are not listening:
The quantum baseball in my example was not a dark matter baseball, I never said it was. ... it was normal matter, so that it could interact as an electron does with other normal matter. Let me repeat this as it is not sinking in: the quantum baseball in my example was purely imaginary with no correspondence to anything in Nature. It was a fiction, it was not real, and this is important: it has nothing to do with dark matter.
You seem to want to imagine a material object, roughly baseball shaped, but with the mass of an electron (or less - since you want the debroglie wavelength to be longer), which does not interact electromagnetically (dark matter). So let's say a sphere the volume of a baseball containing nothing but an electron's mass amount of dark matter. Fine... there is no reason to believe that such a thing is even physically possible, and indications that it isn't. So we are probably positing a situation that violates known laws of physics ... just so you realize that. Do not expect the conclusions to make sense.
Do you realize that such an object has a density somewhat less than that of a vacuum ... it is literally less than nothing. But let's just say ... it can still interact by the weak nuclear interaction, and by gravity. (There are three forces besides the electromagnetic interaction, but current models of dark matter tend to exclude the strong nuclear force as well.)
Now you want to know if such an object, already doubly impossible, can exhibit interference at slits ... well, at this stage, while you are making stuff up why not make that up as well? But OK - the slit experiment involves somehow restricting the possible paths between some dark-matter-baseball emitter, and a detector for same. Whatever is able to restrict the path of such an object must do so by interacting with it somehow.
Does gravity interact in the same way as other quantum mechanical forces?
The short answer is: "we don't know". We do not currently have a working theory of quantum gravity and we are wayy off being able to manipulate dark matter.
It may be that dark matter will provide clues to quantum gravity - ie we can try to do interference experiments with it where the possible paths are restricted by gravitational fields. But: and here is where I want you to hear me: none of this needs a baseball sized lump of dark matter!
I don't understand your obsession with this.
Maybe you are thinking that you want to be able to watch the particle as it travels between source and detector?
We can't know what happen between emission and detection. But for quantum baseball size object with similar deBroglie wavelength as electron. Still we can't know what happens in between? but it's so big...
This is a totally different type of question.
Please understand, we cannot see what happens in between because that would spoil the effect we are trying to watch -
it has nothing at all to do with the physical size of the object in question.
This bit does not need dark matter either - it has nothing to do with dark matter.
We could do the electron interference experiment in something like a cloud chamber where little bubbles trace out the trajectory of the electron.
If the important property of a "macroscopic object" is that you can watch it move and know where it went ... then the electron is now "macroscopic". Better in fact because it leaves a record of where it's been as if the baseball could draw a line in the air as it flew.
But if we do this - then the interference effect vanishes. Guess why?
It is the same for the hypothetical quantum baseball.
There are some other issues with the quantum baseball ... ie. with a normal baseball you know with good precision when it was pitched and when it was caught.
But if you do that with the quantum baseball you lose the interference effect as well... because the energy of the baseball (which affects it's debroglie wavelength) will be very uncertain.
The bottom line is that big objects do not map well to quantum processes ... this is not surprising: if they did, we would not need quantum mechanics in the first place.
