Here's an interesting thought experiment for you.
What happens when you squeeze an object really hard while cooling it down at the same time?
It will of course begin to get denser and denser, changing it's material properties.
Each of these density variation results in what are called phase transitions and all of the following are states of matter as we know them.
At the bottom end, you have bose einstein condensates, a new phase of matter we are just beginning to explore.
Beyond that, you have the everyday states of matter.
Solid, liquid, gas and finally plasma.
At the far end of the scale, you have quark / gluon plasmas.
Objects so energetic that they exist for fractions of a second, and are the domain of our good friend @lemouth who is a particle physicist at CERN where he works on the LHC. He's a literal Quantum Mechanic!
Most highly energetic events eventually end up as gamma rays though.
Gamma rays are just highly energetic photons.
The energy of light is a function of it's wavelength E=hf
A photon with a wavelength equal to the Planck length would have an energy of about 7.671 × 1028 eV or 1.229 × 1010 joules (12.29 gigajoules)
It would be the output of the world's largest power plant, packed into a grain of rice.
You could never manage to eat this grain of rice it would eat you first.
This would be a black hole!
Although that blackhole would evaporate in nanoseconds due to hawking radiation.
Doesn't that make blackholes technically a state of matter?
Or would it really form a blackhole in the first place?
If we use light to look at the structure of an object, we need to have it's wavelength preferably smaller than the size of the details we wish to look at. Probing an object that has a (linear) size equal to the Planck length, requires that the energy of the photon be greater than the mass of a black hole of that "size". So, a classical black hole would prevent us to see details inside that object. We are lead to an apparent contradiction, which suggests an incompatibility between Relativty and Q.M. – André May
One thing about black holes is that any time we say black hole what we are really saying is...
CAUTION!!! HERE THERE BE DRAGONS!
When we start seeing dragons or unicorns in the math, what it really means is that we have reached or possibly exceeded, some fundamental limit to our understanding.
We don't have a theory that unifies QM & Gravity yet. We have a few theories that seem to be getting close, but the point where all our theories begin to break down...?
Blackholes!
Maybe the problem isn't the theories themselves, but the blackholes? What if blackholes don't actually exist?
What if they just represent the place where relativity actually meets quantum mechanics?
What if QM already won the battle over gravity well before we even got there?
Here is what I mean...
When a star collapses, a black hole is hardly the only outcome. The most likely outcome is actually a neutron star. A neutron star is where gravity is so immense that the electrons and protons combine to form neutrons. The neutron star is prevented from further collapse by the pauli exclusion principle.
This is called Neutron Degeneracy pressure. It represents a fundamental limit for most stars.
But at this level, the whole star begins to take on some interesting characteristics.
It is hypothesized that a neutron star acts like a single giant atom.
In otherwords QM effects already are being exhibited at the macroscale and we are nowhere near blackhole levels of density.
Yet if you add more mass, you end up with the hypothesized "Quark" star. Everything at this point has ceased having individual identity and behaves like a single large quark.
Add even more mass and you reach the Chandreskar limit. This is believed to be the point of no return, at this point the whole thing collapses into a black hole.
But what if it just doesn't?
There are theories that a quark star and a bose einstein condensate should behave roughly the same.
Since a BEC represents as close to the absolute 0 point of energy in a material, it is most effected by quantum vacuum fluctuations.
So what if we permit that at the Chandrasekhar limit, space and time are still maximally warped to the point that the escape velocity would need to exceed C, in otherwords we permit an event horizon, but instead of a singularity on the other-side you find what?
Well most likely the densest, coldest material otherwise possible.
A very large, thick shell of bose einstein condensate.
But if it's a shell then what is the shell around?
This is where it gets interesting...
If we accept that the planck length is the smallest length at which anything can be said to "have occurred", and we also accept that photons can in fact be blue shifted to a wavelength shorter than the planck length. Then the only plausible thing that could be there, are bubbles of new space time.
Not just our own space time warped, but literally a whole new universe being constructed at a rate of about 21 micrograms for each photon that happens to fall in. Something like this would be prevented from further collapse by the pressure of the baby universe growing inside of it. Interestingly, this allows for the creation of new energy ex-hilo, you get more energy than is put in.
It violates conservation of energy, but then again so does dark energy. Unless of course, our dark energy, our vacuum energy is coming from a similar process. But that would mean we're inside one of these things too?
This expanding baby universe, represents a new type of degeneracy pressure, which performs a function similar to the neutron degeneracy pressure, but this would be a "spacetime degeneracy pressure". Meanwhile since it would be sustained by gravitational vacuum energy. It would be more rightly called a GRAvitational VAcuum Star or GRAVASTAR
Perhaps then... Here be the dragons?
Further reading...
New Horizons in Gravity: Dark Energy and Condensate Stars
Slowly rotating thin shell gravastars
Construction of higher dimensional charged gravastars
Can accretion disk properties distinguish gravastars from black holes?