Recent content by astromandi

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    Can a Star Exist with Negative Pressure?

    Dark energy behavior would be completely different. Since When we deal with dark energy we have matter(Don`t know weather to call it matter or something else) with negative energy. And we study it`s dynamics in the spatially homogeneous and isotropic universe. Whereas when we deal with...
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    Can a Star Exist with Negative Pressure?

    Why does it have to be a inflating star?? Can be have a star in equilibrium with material with negative pressure?? Suppose we have a star with no pressure atall in will collapse(free fall) If there is a positive pressure then it would try to stop/resist the collapse. If there is a...
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    Can a Star Exist with Negative Pressure?

    Star with negative pressure? Is it possible to have a star with matter with unusual equation of state. Will it be possible to have a star with negative pressure.
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    What happens before crossing the Event Horizon

    Whyso? Light travels at c in all reference frames. All we would see is those signals changing in wavelength. Please read chapter on black holes from Sean Carroll`s book or free online notes on General relativity. This is true that signals would be redshifted. But also they would reach us...
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    What happens before crossing the Event Horizon

    Suppose a person sitting on the object falling into black hole were to emit signal at regular interval in his own reference frame. These signals would reach us at infinity at progressively increasing interval of time.. As the object approaches event horizon , the timing between arrival of two...
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    Is the speed of one beam in the LHC nearly twice that of the other?

    The speed of one beam wrt other is 'c'. NOT 2c
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    Can Newtonian Cosmology Emerge from FRW and Oppenheimer-Snyder Frameworks?

    Yeah right. Time dilation has to be same everywhere since FRW is spatially homogeneous and isotropic at any given epoch. And Time dilation not being same would violate homogeneity. Regarding your calculation of the time dilation When we write down the FRW metric in usual form we work in...
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    Can Newtonian Cosmology Emerge from FRW and Oppenheimer-Snyder Frameworks?

    In this case basically you start with spherically symmetric metric in synchronous coordinate system. And then solve Einstein`s equation both inside and outside star. And it just turns out that solution of the Einstein`s equation inside the star is FRW and outside it`s Scwarschild. So there is...
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    Can Newtonian Cosmology Emerge from FRW and Oppenheimer-Snyder Frameworks?

    In this case we don`t have FRW universe. Ofcourse if entire universe were described by FRW metric then Newtonian limit doesn't make sense. But here we are concerned with spacetime ...only part of it is described by FRW and in my opinion it happens to be Asymptotically flat. But as you...
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    Can Newtonian Cosmology Emerge from FRW and Oppenheimer-Snyder Frameworks?

    The inside of the (collapsing ) matter is a different space-time from the exterior. The interior is not asymptotically flat but the exterior is. Can you please elaborate this. The notion which I have in mind about asymptotically flat spacetime is that as r--> infinity the metric should...
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    Can Newtonian Cosmology Emerge from FRW and Oppenheimer-Snyder Frameworks?

    If the metric outside the star is Schwartzschild then as r --> infinity would be tend to be Minkoski. Hence spacetime as a whole is asymptotically flat(although part of it described by FRW). Hence I guess it would be possible to define Newtonian limit. And there should also be...
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    Can Newtonian Cosmology Emerge from FRW and Oppenheimer-Snyder Frameworks?

    The Newtonian limit for general relativity exists only for the asymptotically flat spacetimes. FRW case definitely not asymptotically flat. SO the Newtonian limit should not exist for it. However we have Newtonian theory of cosmology in homogeneous and isotropic universe. So my question is...
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    Understanding the Violation of Parity in Weak Interactions

    what is meaning of parity. why is the parity violated in weak interaction. what is meaning of maximal violation of parity
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