A Warm' Model of the Early Universe Could Solve Two Cosmic Mysteries at Once

"For a fraction of a second after the big bang occurred 13.8 billion years ago, most physicists believe, the newborn universe dramatically ballooned in size, jumping from being smaller than a proton to being bigger than a softball. Such an exponential expansion may seem minor, but it is equivalent to a grape in the palm of your hand swelling to become tens of thousands of times larger than the observable universe."

"Known as cosmic inflation, this strange, fleeting period is usually considered to have been an expansion of near nothingness because, at the time, most of the universe's elementary particles had yet to blink into existence. In other words, the standard view of cosmic inflation suggests the universe didn't really begin as a hot, dense fireball but rather as a cold void that only later reheated into a plasmatic soup of particles by some poorly understood process."

Cosmic inflation produced an exponential expansion that magnified the newborn universe from subatomic scales to cosmic scales within a fraction of a second. The standard picture treats inflation as a cold expansion followed by a separate reheating into a hot plasma of particles, leaving reheating mechanisms poorly understood. A warm-inflation scenario posits that particle production occurred concurrently with inflation, naturally arising from interactions within the Standard Model. Warm inflation can populate the universe with matter during the expansion and requires only one unconfirmed particle beyond established physics, making the mechanism simple and generically achievable.

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