“How are matter and energy distributed?” I asked. peter schweitzer, a theoretical physicist at the University of Connecticut. “We don’t know.”
Schweitzer has spent most of his career thinking about the gravitational side of protons. Specifically, he is interested in a matrix of proton properties called the energy-momentum tensor. “The energy-momentum tensor knows everything there is to know about particles,” he said.
Albert Einstein’s general theory of relativity posits that the gravitational pull acts on an object as it follows the curve of space-time, dictating how the energy-momentum tensor bends in space-time. For example, we discuss the configuration of energy (or equivalent mass) that accounts for most of the twisting of spacetime. It also tracks information about how momentum is distributed and where compression or expansion occurs, allowing space-time to be slightly curved.
If we could know the shape of spacetime around a proton, Russia and American When physicists worked on their own in the 1960s, they were able to infer all the properties indexed by the energy-momentum tensor. These include the proton’s mass and spin, along with the proton’s pressure and force configuration, a collective property that physicists call the “Drach term” after the German word for pressure. It will be. The term is “as important as mass or rotation, but no one knows what it is,” Schweitzer said, but that’s starting to change.
In the 60s, it looked as if measuring the energy-momentum tensor and calculating the Druck term required a gravitational version of the usual scattering experiment. Shooting a massive particle towards a proton, he causes the two to exchange gravitons (virtual particles). It constitutes gravitational waves, not photons. But because gravity is so weak, physicists expect graviton scattering to occur 39 orders of magnitude less frequently than photon scattering. Experiments cannot detect such weak effects.
“I remember reading about this when I was a student,” he said Volker Burkert, a member of the Jefferson Institute team. The conclusion was that “we probably won’t learn anything about the mechanical properties of the particles.”
gravity without gravity
Gravity experiments are still unimaginable today. However, in the late 1990s and early 2000s, research was carried out by physicists Xiangdong Ji and the late Maxim Polyakov, who were working separately. revealed be Workaround.
The general scheme is: When you shoot an electron lightly at a proton, the electron usually sends a photon to one of the quarks and glances at it. But less than once in a billion times, something special happens. Incoming electrons send photons. The quark absorbs it and releases another photon after a heartbeat. The main difference is that this rare event involves two photons (both an incoming photon and an outgoing photon) instead of one photon. Ji and Polyakov’s calculations showed that if an experimenter could collect the resulting electrons, protons, and photons, from the energy and momentum of these particles he could infer what happened with the two photons. And that two-photon experiment would be essentially as informative as the impossible graviton scattering experiment.
