Recent content by aristurtle

yes,this potential is some quantily of energy density deimension and have absolute value to curve the space time.You can't redifine it by adding a constant. It is an extensive quantity right over there.

sorry I'm non english native speaker.May be may presentation makes you confuse. But what I'm talking about(the sphere thing) is typical textbook stuff.I would not explain textbooks here.

sorry for my ambigious statement. GR is tested only in our solar system,and it's validity all over universe is not sure. Dark energy is confirmed,but Lamda CDM model is not! that's the "two". Yes, exactly,dark energy could be many many many things beside a cosmological constant. yes,you...

you'd better refer to a textbook for Newtonian viewpoint 2. your point,which i call it Newtonian viewpoint 1, can not be found in any book since it is a little heresy , but I agree with you. you can refer to this one for Newtonian contracting in infinite flat space,which is Newtonian...

What about gravitational backreaction to speed up the expansion? if dark energy is cosmological constant ,and GR is always right,Ok, ultimate de sitter stage is doomed. but the two is not exactly confirmed. if dark energy is dynamical ,there is possibility that index of equation of state of dark...

thank you! But why scalar mode perturbation quantum do not have a name ? They do exist in the calculation of primodial perturbations.for example, quanta of mukhanov variable. Can we call it gravikachu ? pikachu pikachu

In the Newtonian framework. infinite space causes paradox!I think.your argument is absolutely right!but,If you change your view a little, still in Newtonian framework,you will get an contracting universe!just imaging a sphere in space ,and the outside mass can not affect the physics inside.and...

I think singularity may be wrong physically , but singularity in open or flat space is wrong logically. What is an infinite space with no volume? A closed space with singlarity is ok if physics admit it. But an open space with 0 scale factor? That's logically impossible I think. BTW, does LQG...

no,sir. standard model does not include graviton. Or else most people here should pack up and looking for new jobs. :-)

I guess nobody knows exactly. Quantum field theory is a theory based on analogy ,if you have an experience on the knowledge structure of some ancient means of medicine ,like chinese medicine,you should know what "analogy" means. in quantum mechanics, we have a microscopic structure at first...

sorry for a stupid question. Is it the quantum for Scalar perturbation or tensor perturbation? I guess they should be treated differently?thank you.

from a scholasticism type analysis , vacuum should not be claimed to be "with out anything", because for "without anything" we get a unique concept of vacuum. But it is not vacuum is not "one" concept. we can have a space time extension in which more than one quantum field exist , one field A...

I think a state of superposition or possessing a definite spin is the same thing for spin.It depends on how you choose the basis vector of hilbert space.But spin mixed state(as sunlight polarization) are different from "definite spin"(or superposition, which is the same thing).

in quantum mechanics , we represent observables as abstract object ,the operator.we can tell the probobility of an observable to be a certain value. in quantum field, we quantize the amplitute of a certain mode(not always Fourier mode,e.g. in curved spacetime) of our field.If you try to...

O, your presentation will drive some particle physics guys crazy.Collider is just a collider, it is the toy that some guys who likes smashing things can make fun of. If you talk to some guy like Veltman (the dynamite prize laureate) about simulateing early universe in LHC, he will kick your ***...