Hssszn
http://hssszn.com/?p=10368

新暗物質粒子候選者如此稠密 幾乎是微型黑洞


他們的質量是質子的十億個十億倍: Jurik Peter/Shutterstock

暗物質佔有組成宇宙所有物質高達6分之5，[#0026ff]很多都和宇宙綁在一塊[/#0026ff](http://hssszn.com/?p=9171)。儘管它的共通性，暗物質的物理本質，截至2016年，依然是難以理解的，只能間接地看到它[#0026ff]戲劇性地影響[/#0026ff](http://hssszn.com/?p=9268)。現在，一項新的研究發表於[#0026ff]物理評論通訊期刊[/#0026ff](http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.101302)，認為暗物質的次原子粒子，每秒10億個穿越你的手，事實上可能是非常的稠密，它們幾乎是快要變成黑洞的邊緣。

以它們旋轉的速度，星系的螺旋手臂應該被拋射到太空，但它們沒有。在說明是重力的影響之後，科學家只能結論出，一定有額外的結合力讓它們的手臂繼續在一起。這個看不見、神秘的"暗物質"，敘述著是它停止這些星系[#0026ff]把自己撕裂[/#0026ff](http://hssszn.com/?p=6285)。

暗物質經常被假設是由和質子一樣重的粒子所組成，但和物質的交互作用[#0026ff]很微弱[/#0026ff](http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino.html)，像是微中子。在上一個世紀，被認為是暗物質的粒子候選者[#0026ff]來來[/#0026ff](http://www.astro.caltech.edu/~george/ay20/eaa-wimps-machos.pdf)又[#0026ff]去去[/#0026ff](http://www.iflscience.com/physics/has-first-dark-matter-particle-been-found)。隨著[#0026ff]大質量弱作用力粒子[/#0026ff](https://www.newscientist.com/article/mg22229712-600-its-crunch-time-for-dark-matter-if-wimps-dont-show/)(weakly interacting massive particles/WIMP)被考慮為競爭領先者之一，這些難以理解的粒子，在理論上是質子質量的100倍，很可能在大爆炸期間被鍛造出來的。

他們弱交互作用的事實，意味著他們可能非常難被科學家偵測到。的確，直到今天，他們還沒有。這意味著眼前WIMPs的存在，特別是作為暗物質粒子的真正身分，是無法被確認的。

然而，這項新研究描述了一個新的數學模式，認為暗物質粒子不真的是WIMPs，而是更加奇怪的東西。它們事實上比微中子更不能與環境有交互作用，但令人震驚的是，每一個獨立粒子的質量是一個質子的10億個10億倍，大約相當於一個普通的人類細胞。


cosmic web宇宙網形狀類似於神經網脈，部分的組合是暗物質的巨絲(massive filament): Sakkmesterke/Shutterstock

如同[#0026ff]Space.com[/#0026ff](http://www.space.com/32295-super-heavy-dark-matter-particle-proposed.html)所報導，根據南丹麥大學(University of Southern Denmark )博士後研究員、研究的一位作者McCullen Sandora所說，在這樣的質量以及依然是次原子的大小，”在變成縮小版黑洞之前，它們將會[稠密的]和最稠密的粒子的差不多。”

在這個被稱為普郎克交互作用暗物質(Planckian interacting dark matter/PIDM)模式，這些不可思議的稠密次原子粒子可以在大爆炸的餘暉下被偵測到。在大爆炸之後不久，有一段時間被稱為”膨脹”時期，片刻的突然[#0026ff]膨脹[/#0026ff](http://hssszn.com/?p=8633)。這個膨脹鋪平了宇宙的物質，以至於每一個方向的物質比例約略相似。

在這段膨脹期間，宇宙冷卻的很多。當擴張突然慢下來，膨脹停止，宇宙"[#0026ff]重新加熱[/#0026ff]“(https://cds.cern.ch/record/303943/files/9605155.pdf)，並且作者認為這些新的PIDM粒子是在這段時間被鍛造出來的。如果是的話，這些超重粒子的產生，會在[#0026ff]宇宙微波背景輻射[/#0026ff](CMBR)(http://hssszn.com/?p=7609)留下[#0026ff]徵兆[/#0026ff](http://hssszn.com/?p=9235)，理論上可以被地球上的偵測器偵測到。

如同他們所說，這項獵捕在進行中。目前，雖然我們依然無法確定地說暗物質到底是甚麼，這項研究在理論堆裏，加入了另一個引人注目的理論。

來源: [#0026ff]Iflscience[/#0026ff](http://www.iflscience.com/physics/new-candidate-particles-dark-matter-are-so-dense-they-are-almost-miniature-black-holes)








iflscience
http://www.iflscience.com/physics/new-candidate-particles-dark-matter-are-so-dense-they-are-almost-miniature-black-holes

New Candidate Particles For Dark Matter Are So Dense They Are Almost Miniature Black Holes


photo credit: They have the mass of 10 billion billion protons. Jurik Peter/Shutterstock

Dark matter comprises up to five-sixths of the total matter in the universe, binding much of it together. Despite its commonality, the physical nature of dark matter, as of 2016, remains elusive, with its dramatic effects only indirectly seen. Now, a new study published in the journal Physical Review Letters suggests that subatomic particles of dark matter, a billion of which pass through your hand every second, may in fact be so dense that they’re on the verge of becoming black holes.

At the speed they rotate, galactic spiral arms should jettison off into space, but they don’t. After accounting for the effect of gravity, scientists can only conclude that there must be an additional binding force keeping these arms together. The invisible, mysterious “dark matter” describes that which stops these galaxies from tearing themselves apart.

Dark matter is often assumed to consist of particles that have the same mass as a proton, but interact extremely weakly with matter, like a neutrino. Candidates for dark matter particles have come and gone in the last century, with WIMPs – weakly interacting massive particles – considered to be one of the frontrunners. These elusive particles are hypothesized to be 100 times the mass of a proton, and would have likely been forged during the Big Bang.

The fact that they are weakly interacting means that they are probably very hard for scientists to detect – indeed, to date, they haven’t been. This means that for now the existence of WIMPs, especially as the true identity of dark matter particles, cannot be confirmed.

This new study though, describing a new mathematical model, suggests that dark matter particles aren’t actually WIMPs, but something even more exotic. They could in fact be far less able to interact with their environment than a neutrino, but astoundingly, each individual particle will have a mass 10 billion billion times more than a proton – about that of an average human cell.


The cosmic web, similar in shape to a neural network, is partly comprised of massive filaments of dark matter. Sakkmesterke/Shutterstock

As reported by Space.com, at this mass and still at subatomic sizes, they will be “about as [dense] as a particle can be before it becomes a miniature black hole,” according to McCullen Sandora, a postdoctoral researcher at the University of Southern Denmark and an author of the study.

In this model, referred to as Planckian interacting dark matter (PIDM), these incredibly dense subatomic particles could be detected in the afterglow of the Big Bang. Soon after the Big Bang there was a period known as “inflation,” a moment of sudden expansion. This smoothed out the matter in the universe so that it is roughly similar in proportion in every direction.

During this inflation, the universe cooled considerably. As the expansion suddenly slowed and inflation ended, the universe “reheated,” and the authors suggest that these new PIDM particles were forged during this time. If so, the birth of these superheavy particles would have left a signature in the cosmic microwave background radiation (CMBR), which is theoretically detectable by Earth-based detectors.

The hunt, as they say, is on. At present, though, we still cannot say for sure what dark matter truly is, and this study adds another compelling theory to the pile.