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The early Universe was a strange place. Early in its history\u2014in the first quintillionth of a second\u2014the entire cosmos was nothing more than a stunningly hot plasma. And, according to researchers at the Massachusetts Institute of Technology (MIT), this soup of quarks and gluons was accompanied by the formation of weird little primordial black holes (PHBs). It\u2019s entirely possible that these long-vanished PHBs could have been the root of dark matter. <\/p>\n
<\/p>\n MIT\u2019s David Kaiser and graduate student Elba Alonso-Monsalve suggest that such early super-charged black holes were very likely a new state of matter that we don\u2019t see in the modern cosmos. \u201cEven though these short-lived, exotic creatures are not around today, they could have affected cosmic history in ways that could show up in subtle signals today,\u201d Kaiser said. \u201cWithin the idea that all dark matter could be accounted for by black holes, this gives us new things to look for.\u201d That means a new way to search for the origins of dark matter.<\/p>\n Dark matter is mysterious. No one has directly observed it yet. However, its influence on regular \u201cbaryonic\u201d matter is<\/em> detectable. Scientists have many suggestions for what dark matter could be, but until they can observe it, it\u2019s tough to tell what the stuff is, exactly. Black holes could be likely candidates. But the mass of all the observable ones isn\u2019t enough to account for the amount of dark matter in the cosmos. However, there may be a connection to black holes after all.<\/p>\n Most of us are familiar with the idea of at least two types of black holes: stellar-mass and supermassive. There is also a population of intermediate-mass black holes, which are rare. The stellar-mass objects form when massive stars explode as supernovae and collapse to form black holes. These exist throughout many galaxies. The supermassive ones aggregate many millions of solar masses together. They form \u201chierarchically\u201d from smaller ones and exist in the hearts of galaxies. The intermediate-mass ones probably form hierarchically as well and could be a hidden link between the other two types.<\/p>\n Black holes have formed throughout the history of the Universe. That\u2019s why the idea of primordial black holes isn\u2019t too much of a surprise, although they remain elusive. In their very primitive state, they\u2019d be ultradense objects with the mass of an asteroid punched down into something the size of an atom. They probably didn\u2019t last very long\u2014maybe another quintillionth of a second. After formation, they either blinked out of existence or got scattered across the expanding Universe.<\/p>\n So, how could these weird PHBs affect the formation of dark matter if they winked in and out of existence so quickly? That\u2019s where Kaiser and his student\u2019s work come in. They suggest that as the first PHBs scattered, they somehow \u201ctugged\u201d on space-time and changed something that could explain dark matter. That same process could have produced even smaller black holes with a curious property called \u201ccolor charge.\u201d And, there\u2019s a dark matter connection. <\/p>\n \u201cColor charge\u201d is a property of quarks and gluons, and it ends up gluing them together. Think of it as a \u201csuper-charge\u201d. Kaiser and Alonso-Monsalve suggest that some of the very early PHBs had this \u201csupercharge\u201d in the same way as the quarks and gluons had it. If that\u2019s true, then the earliest super-color-charged PHBs would have been an entirely new state of matter. We don\u2019t see them around anymore because they likely evaporated a fraction of a second after they spawned. But, their existence was necessary, particularly to the formation of dark matter.<\/p>\n Even during their short life span, however, the earliest supercharged PHBs could have influenced a key cosmological transition: the time when the first atomic nuclei were forged. Those color-charged black holes could have affected the balance of fusing nuclei. And, they could have done it in a way that astronomers might someday detect with future measurements. Such an observation would point convincingly to primordial black holes as the root of all dark matter today.<\/p>\n If those PHBs did exist, what were THEY made of? Unlike other black holes, there\u2019s not much evidence for something like a star or another black hole that \u201cbirthed\u201d these early ones. To figure that one out, Alonso-Monsalve and Kaiser did some exploration. They calculated the PHB formation \u201cera\u201d as happening just after the Big Bang. \u201cTypical\u201d microscopic black holes formed within this short \u201cflash of time.\u201d Those would have been as massive as an asteroid and as small as an atom. But, they also found that a tiny population of exponentially smaller black holes came into being. Those had the mass of a rhino and a size much smaller than a single proton.<\/p>\n This process probably started around one second after the Big Bang. That gave all these PBHs plenty of time to disrupt the equilibrium conditions that would have prevailed when the first nuclei began to form from the quark-gluon plasma. The super-charged black holes would have quickly evaporated. That probably happened about the time when the first atomic nuclei began to form. \u201cThese objects might have left some exciting observational imprints,\u201d Alonso-Monsalve said. \u201cThey could have changed the balance of this versus that, and that\u2019s the kind of thing that one can begin to wonder about.\u201d<\/p>\n The backdrop for the formation of these short-lived black holes? The quark-gluon plasma. And, it should have a distribution of \u201ccolor charge\u201d. Kaiser and Alonso-Monsalve determined the size of an area in the plasma that could collapse to form a PBH. It turns out there wouldn\u2019t have been much color charge in most typical black holes formed in the moment. That\u2019s because they probably formed by absorbing a huge number of regions that had a mix of charges. Thus, they wouldn\u2019t be \u201csupercharged.\u201d<\/p>\n But the smallest black holes would have been highly color-charged. They would have contained the maximum amount of any type of charge allowed for a black hole. And, by their formation, they could well have produced the tiniest bit of change that led to the formation of dark matter. <\/p>\n Exotic Black holes Could be a Byproduct of Dark MatterBlack Holes Through Cosmic Time<\/h3>\n
The Link Between Primordial Black Holes and Dark Matter<\/h3>\n
What Were Those Early PHBs Made Of?<\/h3>\n
From Plasma to PHBs to Dark Matter<\/h3>\n
For More Information<\/h4>\n
Preprint: Primordial Black Holes with QCD Color Charge<\/p>\nLike this:<\/h3>\n