Anıl Zenginoğlu
@anilzen.bsky.social
Scientist working on waves, black holes, hyperbolic geometry, and optimization. Chasing light to infinity. Seeking resonance.
The full letter is here: chronicle.brightspotcdn.com/4c/5e/044424...
chronicle.brightspotcdn.com
February 18, 2025 at 1:34 AM
The full letter is here: chronicle.brightspotcdn.com/4c/5e/044424...
Physics models reality.
If our experience of reality includes the decay of energy due to radiation, the coordinate system we use should respect that.
If our experience of reality includes the decay of energy due to radiation, the coordinate system we use should respect that.
February 6, 2025 at 10:03 PM
Physics models reality.
If our experience of reality includes the decay of energy due to radiation, the coordinate system we use should respect that.
If our experience of reality includes the decay of energy due to radiation, the coordinate system we use should respect that.
A prominent example is energy.
Energy at spatial infinity is conserved in time, but energy evolving along null infinity decays.
This is a physical observable evaluated at the asymptotic limit in different coordinate systems. But the coordinates are related by singular transformations.
Energy at spatial infinity is conserved in time, but energy evolving along null infinity decays.
This is a physical observable evaluated at the asymptotic limit in different coordinate systems. But the coordinates are related by singular transformations.
February 6, 2025 at 10:03 PM
A prominent example is energy.
Energy at spatial infinity is conserved in time, but energy evolving along null infinity decays.
This is a physical observable evaluated at the asymptotic limit in different coordinate systems. But the coordinates are related by singular transformations.
Energy at spatial infinity is conserved in time, but energy evolving along null infinity decays.
This is a physical observable evaluated at the asymptotic limit in different coordinate systems. But the coordinates are related by singular transformations.
The same is true for cosmological horizons and infinity.
Moments of time must be horizon-penetrating if the horizons are at a finite proper distance and hyperboloidal (asymptotically hyperbolic) if they are at infinity.
This also breaks time-reflection symmetry and provides a direction of time.
Moments of time must be horizon-penetrating if the horizons are at a finite proper distance and hyperboloidal (asymptotically hyperbolic) if they are at infinity.
This also breaks time-reflection symmetry and provides a direction of time.
February 6, 2025 at 12:51 PM
The same is true for cosmological horizons and infinity.
Moments of time must be horizon-penetrating if the horizons are at a finite proper distance and hyperboloidal (asymptotically hyperbolic) if they are at infinity.
This also breaks time-reflection symmetry and provides a direction of time.
Moments of time must be horizon-penetrating if the horizons are at a finite proper distance and hyperboloidal (asymptotically hyperbolic) if they are at infinity.
This also breaks time-reflection symmetry and provides a direction of time.
After Schwarzschild discovered the first black-hole solution of the Einstein equations in 1915, it took about 50 years to recognize that time must be redefined in the presence of horizons.
The Schwarzschild "singularity" is due to the wrong definition of time, which assumes synchronization.
The Schwarzschild "singularity" is due to the wrong definition of time, which assumes synchronization.
February 6, 2025 at 12:51 PM
After Schwarzschild discovered the first black-hole solution of the Einstein equations in 1915, it took about 50 years to recognize that time must be redefined in the presence of horizons.
The Schwarzschild "singularity" is due to the wrong definition of time, which assumes synchronization.
The Schwarzschild "singularity" is due to the wrong definition of time, which assumes synchronization.
Time must be defined differently when there are horizons in space.
Our usual definition of time across space implicitly assumes synchronization via two-way communication.
Horizons only allow one-way communication, so time must be adapted to one-way communication.
Our usual definition of time across space implicitly assumes synchronization via two-way communication.
Horizons only allow one-way communication, so time must be adapted to one-way communication.
February 6, 2025 at 12:51 PM
Time must be defined differently when there are horizons in space.
Our usual definition of time across space implicitly assumes synchronization via two-way communication.
Horizons only allow one-way communication, so time must be adapted to one-way communication.
Our usual definition of time across space implicitly assumes synchronization via two-way communication.
Horizons only allow one-way communication, so time must be adapted to one-way communication.
So, horizons exist even in flat spacetime where there's no gravity or expansion of space.
If we're interested in large-scale phenomena (propagation of waves across large distances, for example), we should consider horizons. We didn't notice them before because they are far away.
If we're interested in large-scale phenomena (propagation of waves across large distances, for example), we should consider horizons. We didn't notice them before because they are far away.
February 6, 2025 at 12:51 PM
So, horizons exist even in flat spacetime where there's no gravity or expansion of space.
If we're interested in large-scale phenomena (propagation of waves across large distances, for example), we should consider horizons. We didn't notice them before because they are far away.
If we're interested in large-scale phenomena (propagation of waves across large distances, for example), we should consider horizons. We didn't notice them before because they are far away.
But there are other horizons.
Because of the expansion of space, there is a limiting surface beyond which we can never see. That's the cosmological horizon.
Infinity is another one. You can send radiation to infinity but can never receive it.
Because of the expansion of space, there is a limiting surface beyond which we can never see. That's the cosmological horizon.
Infinity is another one. You can send radiation to infinity but can never receive it.
February 6, 2025 at 12:51 PM
But there are other horizons.
Because of the expansion of space, there is a limiting surface beyond which we can never see. That's the cosmological horizon.
Infinity is another one. You can send radiation to infinity but can never receive it.
Because of the expansion of space, there is a limiting surface beyond which we can never see. That's the cosmological horizon.
Infinity is another one. You can send radiation to infinity but can never receive it.
Hi! I'm a physicist working in general relativity with occasional math. Please add me to the feed. Thanks!
scholar.google.com/citations?us...
scholar.google.com/citations?us...
Anıl Zenginoğlu
University of Maryland - Cited by 2,783 - Wave Equations - Gravitational Waves - Kalman Filters - Fluid Dynamics
scholar.google.com
November 23, 2024 at 6:12 PM
Hi! I'm a physicist working in general relativity with occasional math. Please add me to the feed. Thanks!
scholar.google.com/citations?us...
scholar.google.com/citations?us...
It’s a two-way street. I believe there is work to be done at the classical level before we can understand the quantum.
November 23, 2024 at 11:35 AM
It’s a two-way street. I believe there is work to be done at the classical level before we can understand the quantum.
What is time across space?
How do you construct a natural surface of simultaneity as a distant observer?
Does understanding time give us a hint about the quantum nature of gravity?
How do you construct a natural surface of simultaneity as a distant observer?
Does understanding time give us a hint about the quantum nature of gravity?
November 23, 2024 at 9:04 AM
What is time across space?
How do you construct a natural surface of simultaneity as a distant observer?
Does understanding time give us a hint about the quantum nature of gravity?
How do you construct a natural surface of simultaneity as a distant observer?
Does understanding time give us a hint about the quantum nature of gravity?
I use these two images in my lecture on Qubits.
Even experts sometimes confuse the map with the territory.
Even experts sometimes confuse the map with the territory.
November 22, 2024 at 4:56 PM
I use these two images in my lecture on Qubits.
Even experts sometimes confuse the map with the territory.
Even experts sometimes confuse the map with the territory.
I'm most excited about the connection of hyperboloidal surfaces to holography. There are a few calculations to be made on that front, so stay tuned.
November 22, 2024 at 4:45 PM
I'm most excited about the connection of hyperboloidal surfaces to holography. There are a few calculations to be made on that front, so stay tuned.