Prof. Dr. Ali Övgün Chair of the Conference on Gravitational Aspects of Lorentz Violation

Prof Ali Ovgun Chair of Session at the Conference on Celebrated Aspects of Lorentz Violation
Prof Ali Ovgun Chair of Session at the Conference on Celebrated Aspects of Lorentz Violation

The Department of Physics at Indiana University in Bloomington, Indiana held the Second IUCSS Lorentz Violation Workshop on Gravitational Aspects as an online conference March 13-14, 2023. The second day of the workshop coincides with Albert Einstein's 144th birthday.

Focusing on EFT techniques and gravitational SME, the workshop mainly deals with perturbative Lorentz and diffeomorphism refraction theory in gravitational contexts. In addition to reviewing and discussing relevant topics in this intense field, we will also look at potential areas of research. Short live broadcast presentations will be part of the workshop format along with discussion time.

One of the Turkish scientists, Associate Professor Ali Övgün, took his place in the workshop as the chair of the session. He has many publications on these subjects. Associate Professor Ali Övgün continues his studies and academic life at Eastern Mediterranean University.

Now we would like to convey some information about the subject to you.

Scientists have discovered a new technique to test the long-held belief that the universe is the same in every way. This is what we might call observing the shadow of a black hole. If the shadow is slightly smaller than current physics theories predict, this could support the bumblebee theory of gravity, which predicts what would happen if the seemingly perfect symmetry of the universe was actually not that perfect.

If researchers can find a black hole with such a small shadow, it could lead to an entirely new theory of gravity and potentially even shed light on why the universe is expanding so fast.

Symmetry is loved by physicists because it enables us to understand some of the deepest mysteries of the universe. For example, physicists have discovered that you can change your test equipment even if you get the same results from an experiment on basic physics.

In other words, wherever you do the experiment in space, the result of the experiment will be the same. This comes right after the law of conservation of momentum from a mathematical point of view.

Another example: If you do your experiment once, wait a while, and then repeat, the result will be the same (again, all things equal). The law of conservation of energy, which states that energy can neither be created nor destroyed, is closely related to this temporal symmetry.

Another important symmetry is the basis of contemporary physics. It's known as the "Lorentz" symmetry, in honor of the physicist Hendrik Lorentz, who discovered all this in the early 1900s. It turns out that if you reversed your experiment, you would still get the same result (all else being equal). If you increase it to a constant speed, the result of your experiment will still be the same.

In other words, all other things being equal, the result of an experiment performed completely still and at half the speed of light will be the same.

The principles of physics are the same regardless of position, time, orientation, and velocity. This is the symmetry that Lorentz discovered.

What can we deduce from this fundamental symmetry? First, we have Einstein's complete theory of special relativity, which sets a constant speed of light and explains how objects moving at different speeds are related to space and time.

Wasp Gravity 

The principles of special relativity are so fundamental to physics that they can almost be considered a super theory of physics. If you want to develop your own theory of how the world works, it must be consistent with these principles.

Or shouldn't be.

Physicists are constantly working to develop new and improved physical theories, as older theories such as general relativity and the Standard Model of particle physics, which explain how matter warps space-time, fall short of explaining everything in the universe, including what happens at the center of a black hole. Checking whether beloved concepts such as Lorentz symmetry are true in extreme cases is another fruitful place to look for new physics.

According to some gravitational theories, the universe may not actually be perfectly symmetrical. According to these ideas, the cosmos has additional components that force it to deviate from Lorentz symmetry from time to time. In other words, the universe may have a unique or preferred orientation.

These brand new models explain a theory known as wasp gravity. The term is thought to derive from scientists' assertion that bumblebees should not be allowed to fly because we do not understand how their wings generate lift. While these gravity models stand out as potential aspects of new physics, we have a limited understanding of how they work and how they might be consistent with the universe we can observe.

Perhaps one of the most effective uses of bumblebee gravity models is to explain dark energy, which is responsible for the observed accelerated expansion of the universe. It turns out that an effect that causes accelerated expansion may be linked to how much our universe deviates from Lorentz symmetry. And since we don't know what creates dark energy, this hypothesis seems pretty compelling.

Dark Silhouette

You now have a popular new theory of gravity built on groundbreaking concepts like violation of symmetry.

How would you test this theory? By traveling to a black hole where gravity is maximized.

The researchers' paper was published in Physical Revivew D 103, 044002 (2021). The researchers studied the shadow of a black hole in an imaginary universe that was constructed to be as realistic as possible.

Also work by Associate Professor Ali Övgün and Xiao-Mei Kuang Annals of Physics 447 (2022) 169147 “Strong gravitational lensing and shadow constraint in M87 of slowly rotating Kerr-like black hole” (Strong gravitational lensing and shadow constraint from M87* of slowly rotating Kerr-like black hole).

In addition, another study by İbrahim Güllü and Ali Övgün is “Annals of Physics 436, 168721 (2022) Schwarzschild-like black hole with a topological defect in bumblebee gravity”.

(Remember the first photo of the M87 black hole taken by the Event Horizon Telescope just a year ago? The region absorbing all light from around and behind the black hole was that hauntingly beautiful dark void at the center of the dazzling ring).

The team built an accelerating black hole (just as we see it) against the background of an expanding universe and changed the degree of symmetry violation to match the behavior of dark energy, which scientists can measure, to make the model as realistic as possible.

They discovered that in this scenario, a black hole's shadow could be up to 10% smaller than it would be in a "normal gravity" world, providing a clear tool for assessing wasp gravity. Even if the current image of the M87 black hole is too blurry to distinguish them, efforts are being made to capture better images of more black holes, allowing scientists to further investigate some of the universe's biggest enigmas.

Source: LiveScience


Günceleme: 15/03/2023 15:57

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