Scientists Reveal New Connections Between Small Particles and the Vast Universe

Tuesday, July 25, 2017

Scientists Reveal New Connections Between Small Particles and the Vast Universe

Scientists Reveal New Connections Between Small Particles and the Vast Universe:

The cosmos can be considered as a collider for human to access the results of particle physics experiments at ultimate high energies. Credit: Department of Physics, HKUST

Our observable universe is the largest object that physicists study: It spans a diameter of almost 100 billion light years. The density correlations in our universe, for example, correlations between numbers of galaxies at different parts of the universe, indicate that our vast universe has originated from a stage of cosmic inflation.

On the other hand, elementary particles are the smallest object that physicists study. A particle physics Standard Model (SM) was established 50 years ago, describing all known particles and their interactions.

Are density distributions of the vast universe and the nature of smallest particles related? In a recent research, scientists from the Hong Kong University of Science and Technology (HKUST) and Harvard University revealed the connection between those two aspects, and argued that our universe could be used as a particle physics "collider" to study the high energy particle physics. Their findings mark the first step of cosmological collider phenomenology and pave the way for future discovery of new physics unknown yet to mankind.

The research was published in the journal Physical Review Letters on June 29, 2017 (doi:10.1103/PhysRevLett.118.261302) and the preprint is available online (https://arxiv.org/abs/1610.06597).

"Ongoing observations of cosmological microwave background and large scale structures have achieved impressive precision, from which valuable information about primordial density perturbations can be extracted, " said Yi Wang, a co-author of the paper and an assistant professor at HKUST's department of physics. "A careful study of this SM background would be the prerequisite for using the cosmological collider to explore any new physics, and any observational signal that deviates from this background would then be a sign of physics beyond the SM."

The team carried out a two-step task to work out the background of the SM model. The first step was to work out the SM spectrum during inflation, which turned out to be dramatically different from that obtained from the particle physics calculation in flat space. The second one was to figure out how the SM fields entered the cosmological density correlation functions.

"Just like the line pattern of the light you see when observing a mercury lamp through a spectrometer, the mass distribution of the fundamental particles in SM also presents a special pattern, or a 'mass spectrum', which can be viewed as the fingerprint of SM," explained Zhong-Zhi Xianyu, a co-author and physicist at Center for Mathematical Sciences and Applications in Harvard University, "However, this fingerprint is subject to change if we change the ambient conditions. Just like the light spectrum changes when applying strong magnetic field to the lamp, the spectrum of the SM particles turns out to be very different at the time of inflation from it is now due to the inflationary background." The team carefully examined all effects from inflation and showed how the mass spectrum of SM would look like for different inflation models.

"Through inflation, the spectrum of elementary particles is encoded in the statistics of the distribution of the contents of the universe, such as the galaxies and cosmic microwave background, that we observe today", explains Xingang Chen, a co-author and scientist in the Harvard-Smithsonian Center for Astrophysics. "This is the connection between the smallest and largest."

Many problems along this direction remain to be explored. "In our minimal setup, the Standard Model particles interact with the inflaton (the driving force of inflation) rather weakly. But if some new particles can mediate stronger interactions between these two sectors, we would expect to observe a stronger signal of new physics," said Wang. "The cosmological collider is an ideal arena for new physics beyond SM."

Credit: eurekalert.org

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The National Aeronautics and Space Administration (NASA) is the United States government agency responsible for the civilian space program as well as aeronautics and aerospace research. President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA's predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

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The Oxford English Dictionary defines a UFO as "An unidentified flying object; a 'flying saucer'." The first published book to use the word was authored by Donald E. Keyhoe. The acronym "UFO" was coined by Captain Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs. He wrote, "Obviously the term 'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO (pronounced Yoo-foe) for short." Other phrases that were used officially and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable object", and "flying saucer". The phrase "flying saucer" had gained widespread attention after the summer of 1947. On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold timed the sighting and estimated the speed of discs to be over 1,200 mph (1,931 km/h). At the time, he described the objects' shape as being somewhat disc-like or saucer-like, leading to newspaper accounts of "flying saucers" and "flying discs". In popular usage the term UFO came to be used to refer to claims of alien spacecraft. and because of the public and media ridicule associated with the topic, some investigators prefer to use such terms as unidentified aerial phenomenon (or UAP) or anomalous phenomena, as in the title of the National Aviation Reporting Center on Anomalous Phenomena (NARCAP).

UFO PHOTO PHOTOGRAPHY

UFO - Unidentified Flying Object An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, and have become popular subjects in fiction. While UFOs are often later identified, sometimes identification may not be possible owing to the usually low quality of evidence related to UFO sightings (generally anecdotal evidence and eyewitness accounts). Stories of fantastical celestial apparitions have been told since antiquity, but the term "UFO" (or "UFOB") was officially created in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects" (see Air Force Regulation 200-2). During the late 1940s and through the 1950s, UFOs were often referred to popularly as "flying saucers" or "flying discs". The term UFO became more widespread during the 1950s, at first in technical literature, but later in popular use. UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security. Various studies have concluded that the phenomenon does not represent a threat to national security nor does it contain anything worthy of scientific pursuit (e.g., 1951 Flying Saucer Working Party, 1953 CIA Robertson Panel, USAF Project Blue Book, Condon Committee).

Photos of Nature | Nature Photography What is The Universe

Photos of Nature | Nature Photography What is The Universe

Tuesday, July 25, 2017