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Category: cosmology – Page 149

There is a lot of speculation about the end of the universe. Humans love a good ending after all. We know that the universe started with the Big Bang and it has been going for almost 14 billion years. But how the curtain call of the cosmos occurs is not certain yet. There are, of course, hypothetical scenarios: the universe might continue to expand and cool down until it reaches absolute zero, or it might collapse back onto itself in the so-called Big Crunch. Among the alternatives to these two leading theories is “vacuum decay”, and it is spectacular – in an end-of-everything kind of way.

While the heat death hypothesis has the end slowly coming and the Big Crunch sees a reversal of the universe’s expansion at some point in the future, the vacuum decay requires that one spot of the universe suddenly transforms into something else. And that would be very bad news.

There is a field that spreads across the universe called the Higgs field. Interaction between this field and particles is what gives the particles mass. A quantum field is said to be in its vacuum state if it can’t lose any energy but we do not know if that’s true for the Higgs field, so it’s possible that the field is in a false vacuum at some point in the future. Picture the energy like a mountain. The lowest possible energy is a valley but as the field rolled down the slopes it might have encountered a small valley on the side of that mountain and got stuck there.

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“It’s an interesting question to ask: Are there things other than a black hole” that “will give you a hint about what new physics could look like?” added Bah. “But before you get there, you need to know how to tell whether you have a black hole or not, and to do that you have some prototype examples of things that are not black holes to be able to compare.”

Black holes are among the most fascinating and puzzling objects ever observed in our universe. These massive compact entities have so much gravitational power that nothing, not even light, can escape beyond their borders, known as the event horizon. Scientists have imaged black holes with the Event Horizon Telescope and have captured the ripples that these objects make in spacetime, which are called gravitational waves.

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What happened before the Big Bang? In two of our previous films we examined cyclic cosmologies and time travel universe models. Specially, the Gott and Li Model https://www.youtube.com/watch?v=79LciHWV4Qs) and Penrose’s Conformal Cyclic Cosmology https://www.youtube.com/watch?v=FVDJJVoTx7s). Recently Beth Gould and Niayesh Afshordi of the Perimeter Institute for Theoretical Physics have fused these two models together to create a startling new vision of the universe. In this film they explain their new proposal, known as Periodic Time Cosmology.

0:00 Introduction.
0:45 NIayesh’s story.
1:15 Beth’s story.
2:25 relativity.
3:26 Gott & Li model.
6:23 origins of the PTC model.
8:17 PTC periodic time cosmology.
10:55 Penrose cyclic model.
13:01 Sir Roger Penrose.
14:19 CCC and PTC
15:45 conformal rescaling and the CMB
17:28 assumptions.
18:41 why a time loop?
20:11 empirical test.
23:96 predcitions.
26:19 inflation vs PTC
30:22 gravitational waves.
31:40 cycles and the 2nd law.
32:54 paradoxes.
34:08 causality.
35:17 immortality in a cyclic universe.
38:02 eternal return.
39:21 quantum gravity.
39:57 conclusion.

Elizabeth Gould has asked to make this clarification in the written text ” “Despite the availability of infinite time in the periodic time model, this doesn’t lead to thermalization in a typical time-evolution scenario, and therefore doesn’t, strictly speaking, solve the problem related to thermalization in the power spectrum. The reason for this is that, unlike bounce models with a net expansion each cycle, our model has an effective contraction during the conformal phases. Periodic time, therefore, has a unique character in which it reuses the power spectrum from the previous cycles, which is confined to a given form due to the constraints of the system, rather than removing the old power spectrum and needing to produce a new one.”

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What happens if dark-matter particles are produced inside a jet of Standard-Model particles? This leads to a novel detector signature known as semi-visible jets! The ATLAS Collaboration has come up with the first search for semi-visible jets, looking for them in a general production mode where two protons interact by exchanging an intermediate particle, which is then converted into two jets.

The elusive nature of dark matter remains one of the biggest mysteries in particle physics. Most of the searches have so far looked for events where a “weakly interacting” dark-matter particle is produced alongside a known Standard-Model particle. Since the dark-matter particle cannot be seen by the ATLAS detector, researchers look for an imbalance of transverse momentum (or “missing energy”).

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We’ve probably all heard the phrase you can’t make something from nothing. But in reality, the physics of our universe isn’t that cut and dry. In fact, scientists have spent decades trying to force matter from absolutely nothing. And now, they’ve managed to prove that a theory first shared 70 years ago was correct, and we really can create matter out of absolutely nothing.

The universe is made up of several conservation laws. These laws govern energy, charge, momentum, and so on down the list. In the quest to fully understand these laws, scientists have spent decades trying to figure out how to create matter – a feat that is far more complex than it even sounds. We’ve previously turned matter invisible, but creating it out of nothing is another thing altogether.

There are many theories on how to create matter from nothing – especially as quantum physicists have tried to better understand the Big Bang and what could have caused it. We know that colliding two particles in empty space can sometimes cause additional particles to emerge. There are even theories that a strong enough electromagnetic field could create matter and antimatter out of nothing itself.

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A new supernova has turned into the most watched phenomenon in the May night sky. The close proximity of the stellar explosion and the vast amount of observations gathered since the discovery promise to advance astronomers’ understanding of stellar evolution and could even lead to major advances in supernova forecasting.

Supernovas are powerful explosions in which very massive stars, at least eight times more massive than our sun, die when they use up all the hydrogen fuel in their cores. The discovery of this latest exploding star, known officially as 2023ifx, was a serendipitous one.

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New studies reveal that the universe originated with a Big Bang rather than a bouncing phenomenon, challenging previous theories.

The viability of a bouncing universe, a cosmological theory proposing that our universe formed from the contraction and subsequent expansion of a prior universe, has been questioned in a recent study by two publications published by experts.

The new investigations support the idea that the universe’s expansion and contraction may have occurred only once, contrary to the bouncing universe theories’ assertion that this cycle may have happened.

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After three years of upgrading and waiting, due in part to the coronavirus pandemic, the Laser Interferometer Gravitational-wave Observatory has officially resumed its hunt for the signatures of crashing black holes and neutron stars.

“Our LIGO teams have worked through hardship during the past two-plus years to be ready for this moment, and we are indeed ready,” Caltech physicist Albert Lazzarini, the deputy director of the LIGO Laboratory, said in a news release.

Lazzarini said the engineering tests leading up to today’s official start of Observing Run 4, or O4, have already revealed a number of candidate events that have been shared with the astronomical community.

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