# Tag Info

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This might not be right, but as I understand it, the particle and anti particle both have mass. The tidal force of the black hole is able to separate the 2 particles, one of them, flying off in to space, the other, flying towards the black hole. So from inside the event horizon you'd see both particles, well, you'd have to look very close cause particles ...

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Unfortunately, A complete theory of Hawking radiation does not exist at the moment. Hawking radiation is described by a sort of WKB approximation far from the balck hole horizon. In order to describe the phenomenon in the whole space time, in fact we would need a complete theory of Quantum gravity, or at least, a consistent theory (that means with a generic ...

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If $\Omega +\Lambda =1$ then it will be proved that universe is flat. If $\Omega<1$ then universe will fall. if $\Omega>1$ then universe is contractimg.

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The stress-energy tensor that general relativity uses includes a three by three matrix that signifies pressure and stress. It's not clear if you count things that are under tension in one direction and pressure in another as positive or negative pressure, but if the matrix is negative definite, meaning that the object is being pulled apart to some degree in ...

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Besides negative gauge pressure (that could be defined as tension), there are already a couple of great answers with examples of negative pressures from John Rennie and from Dan. In fundamental physics, in the so-called bag models a negative pressure is also introduced in the stress-energy tensor to preserve Lorentz invariance: the physical meaning is ...

2

Pressure is the (outwardly directed) force normal to any area. This definition most naturally fits hydrostatic pressure, e.g. in gases and liquids. In ideal media, this kind of pressure is never negative. In real media, that is not necessarily true. The most obvious example occurs at the boundary of just about any liquid: There a negative pressure acts on ...

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You are not missing anything, apart from a slight misinterpretation of the type Ia supernova cosmology results. With no dark energy, the rate of expansion of the Universe would slow down. The gravitational "pull" of everything would be responsible for this de-celeration. When we look at a distant galaxy, we see it as it was when the light was emitted. ...

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The Mie–Gruneisen equation of state for solids http://en.wikipedia.org/wiki/Mie%E2%80%93Gruneisen_equation_of_state is a model that combines the thermal pressure components and "cold" components of the pressure where the latter is derived thermodynamically from a model intermolecular potential. It has the form $p = p_T(\rho_0,T) + p_c(\rho_0,\chi)$, where ...

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You could probably get a negative pressure in polymer physics, so you could view a big block of rubber as behaving this way. Basically: negative pressures happen when an increase in volume causes a decrease in entropy. Polymers might be a good example because you have these molecules which "want" to be tangled up and kinked ("want" in the sense of "it is ...

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is there a flaw in my considerations? For one thing, the universe is not just empty space. But, anyways... yeah, if you have a volume of constant energy density and you increase that volume while keeping the energy density constant then... yeah, you increase the energy. It's true.

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As noted dark energy is a catch all term to explain accelerated expansion. In most general terms dark energy must be of a form such: ($\rho_{dark \: energy} + \rho_{all \: other \: matter}) + 3(P_{dark \: energy} + P_{all \: other \: matter}) <0$ Where $\rho$ is energy density and $P$ is pressure (they have the same units). As all other terms are ...

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Short and sweet: A cosmological constant is the special case of dark energy with constant density; Dark Energy may also be non-constant, we do not know if this is actually the case.

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Time is affected noticeably by gravity only in strong gravitational fields, i.e. in the vicinity of compact objects, so time doesn't run differently in voids from average regions. Dark matter (DM) and energy (DE), on the other hand, can to some extend be unveiled by studying voids. The morphology of the voids is affected by the nature of the DE, so ...

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