What happens in a universe with only one object as time goes to infinity?

Besides the case of that object being/becoming a blackhole. Perhaps a moon or planet sized object in a universe with nothing else in it. Assuming a universe with laws like ours. Will it somehow evaporate away over time with some sort of quantum decay or stay a frozen mass forever? Could Hawkins radiation work using another force (strong, weak, EM) other than gravity to evaporate it?

I guess it would rip itself apart if it’s the only mass, but besides the case of the expanding/changing spacetime what happens?

Not a physicist, but child prodigy/ Nobel Laureate Chandrasekhar worked on this problem and there is the Chandrasekhar limit : Stars with mass more than 1.4 Solar Mass will burst into Super Novae while the ones with less mass will remain white dwarfs forever

I know the article says stellar-mass objects, but I don’t see why it shouldn’t apply to smaller ones.

It doesn’t apply to an object smaller than stellar mass because the “iron star” is the core of a dead star, which by definition is stellar-mass. The iron is produced by nuclear fusion, which requires stellar mass and its gravity to proceed.

A loaf of bread left alone in an empty universe will not spontaneously collapse into a lump of iron, no matter how long you leave it alone.

The main problem is that your cite isn’t relevant to the OP’s hypothetical, which is a single isolated object of substantially less than stellar mass.

So the grand sweeping cosmological answers don’t apply, because cosmology assumes that less-than-stellar-mass concentrations of matter will eventually be consumed by stars. In OP’s hypothetical, that can’t happen.

I thought, given infinite time, fusion and fission will happen to all matter that isn’t iron anyway, until it’s all iron. Does any element have a half-life approaching infinity?

And I am saying that ut should wirk for a planet or loaf of bread, too. Which is what I said.

The only mention of substellar masses (planet, moon, loaf of bread) in the wiki article is in the section about how it goes if protons and neutrons can decay:

The other half of the wiki (if nucleons don’t decay) and the other article doesn’t address substellar objects at all.

Fusion, even quantum tunneled cold fusion, requires some force to bring nuclei into proximity for fusion to occur (to overcome repulsion). In nature, that has to be gravity, and that requires a minimum mass: stellar mass.

It is conjectured that protons and neutrons will decay with a half-life in excess of 10^{30} years. If that is correct, then the universe will be full of electrons, quarks, and other subnuclear particles. All black holes will have long since decayed via Hawking radiation. This process is expected to take something like 10^{120} years,

What process would take 10^120 years? The largest known black holes would take “only” around 10^97 years, and I don’t know of anything that would take longer.

For all the nucleons to decay (assuming half-lives on the order of 10^{30} years. Yes, 10^{30} is an infinitesimal fraction of 10^{97}, but there are an awful lot of protons and neutrons around. And only half decay in one half-life.

Huh? The number of protons in the observable universe is around the order of 1080. The number of halvings needed to bring that number below 1 is roughly log2(1080) ≈ 266.

Then the time required is 266 x 1030 years ≈ 2.66 x 1032 years, way off from either 1097 or 10120 years.