Some supersymmetric theories require a cosmological constant that is exactly zero, which further complicates things. This is the cosmological constant problem, the worst problem of fine-tuning in physics: there is no known natural way to derive the tiny cosmological constant used in cosmology from particle physics. 0700神も仏も名無しさん2018/07/22(日) 04:16:24.60ID:HO9z7ouw>>696 見える部分とダークマターの線引きがはっきりしたわけだ 0701神も仏も名無しさん2018/07/22(日) 04:17:13.69ID:Su354pOa 宇宙定数問題では、観測されているダークエネルギーは予想されている量を圧倒的に下回る
https://en.wikipedia.org/wiki/Cosmological_constant_problem In cosmology, the cosmological constant problem or vacuum catastrophe is the disagreement between the observed values of vacuum energy density (the small value of the cosmological constant) and theoretical large value of zero-point energy suggested by quantum field theory.
Depending on the Planck energy cutoff and other factors, the discrepancy is as high as 120 orders of magnitude, [1] a state of affairs described by physicists as "the largest discrepancy between theory and experiment in all of science"[1] and "the worst theoretical prediction in the history of physics."[2] 0702神も仏も名無しさん2018/07/22(日) 04:20:26.47ID:Su354pOa>>700
Smolin–Susskind debate The Smolin–Susskind debate refers to the series of intense postings in 2004 between Lee Smolin and Susskind, concerning Smolin’s argument that the "anthropic principle cannot yield any falsifiable predictions, and therefore cannot be a part of science."[36] It began on July 26, 2004, with Smolin's publication of "Scientific alternatives to the anthropic principle". Smolin e-mailed Susskind asking for a comment. Having not had the chance to read the paper, Susskind requested a summarization of his arguments. Smolin obliged, and on July 28, 2004, Susskind responded, saying that the logic Smolin followed "can lead to ridiculous conclusions".[36] The next day, Smolin responded, saying that "If a large body of our colleagues feels comfortable believing a theory that cannot be proved wrong, then the progress of science could get stuck, leading to a situation in which false, but unfalsifiable theories dominate the attention of our field." This was followed by another paper by Susskind which made a few comments about Smolin's theory of
"cosmic natural selection".[37]
The Smolin-Susskind debate finally ended with each of them agreeing to write a final letter which would be posted on the edge.org website, with three conditions attached: (1) No more than one letter each; (2) Neither sees the other's letter in advance; (3) No changes after the fact. 0707神も仏も名無しさん2018/07/22(日) 05:53:53.68ID:Su354pOa>>705
Eternal Inflation With Non-Inflationary Pocket Universes Jean-Luc Lehners1 1Max-Planck-Institute for Gravitational Physics https://arxiv.org/pdf/1206.1081.pdf
Eternal inflation produces pocket universes with all physically allowed vacua and histories. Some of these pocket universes might contain a phase of slow-roll inflation, some might undergo cycles of cosmological evolution and some might look like the galilean genesis or other “emergent” universe scenarios. Which one of these types of universe we are most likely to inhabit depends on the measure we choose in order to regulate the infinities inherent in eternal inflation. We show that the currently leading measure proposals, namely the global light-cone cut-off and its local counterpart, the causal diamond measure, as well as closely related proposals, all predict that we should live in a pocket universe that starts out with a small Hubble rate, thus favoring emergent and cyclic models. Pocket universes which undergo cycles are further preferred, because they produce habitable conditions repeatedly inside each pocket. 0709神も仏も名無しさん2018/07/22(日) 07:58:43.81ID:Su354pOa プランクがインフレーション問題において喜劇をまき起こしていることを考えると 標準モデルが数ある仮説でもかなりマシだと言える
Recent results from the Planck satellite combined with earlier observations from WMAP, ACT, SPT and other experiments eliminate a wide spectrum of more complex inflationary models and favor models with a single scalar field, as reported by the Planck Collaboration. More important, though, is that all the simplest inflaton models are disfavored statistically relative to those with plateau-like potentials. We discuss how a restriction to plateau-like models has three independent serious drawbacks: it exacerbates both the initial conditions problem and the multiverse-unpredictability problem and it creates a new difficulty that we call the inflationary "unlikeliness problem." Finally, we comment on problems reconciling inflation with a standard model Higgs, as suggested by recent LHC results. In sum, we find that recent experimental data disfavors all the best-motivated inflationary scenarios and introduces new, serious difficulties that cut to the core of the inflationary paradigm. Forthcoming searches for B-modes, non-Gaussianity and new particles should be decisive.
Lambda CDM model Since the late 1980s or 1990s, most cosmologists favor the cold dark matter theory (specifically the modern Lambda-CDM model) as a description of how the Universe went from a smooth initial state at early times (as shown by the cosmic microwave background radiation) to the lumpy distribution of galaxies and their clusters we see today — the large-scale structure of the Universe. The theory sees the role that dwarf galaxies played as crucial, as they are thought to be natural building blocks that form larger structures, created by small-scale density fluctuations in the early Universe.[5]
https://en.wikipedia.org/wiki/Lambda-CDM_model#Successes Successes In addition to explaining pre-2000 observations, the model has made a number of successful predictions: notably the existence of the baryon acoustic oscillation feature, discovered in 2005 in the predicted location; and the statistics of weak gravitational lensing, first observed in 2000 by several teams. The polarization of the CMB, discovered in 2002 by DASI [9] is now a dramatic success: in the 2015 Planck data release,[10] there are seven observed peaks in the temperature (TT) power spectrum, six peaks in the temperature-polarization (TE) cross spectrum, and five peaks in the polarization (EE) spectrum. The six free parameters can be well constrained by the TT spectrum alone, and then the TE and EE spectra can be predicted theoretically to few-percent precision with no further adjustments allowed: comparison of theory and observations shows an excellent match. 0711神も仏も名無しさん2018/07/22(日) 08:17:28.16ID:Su354pOahttps://en.wikipedia.org/wiki/Conformal_cyclic_cosmology The conformal cyclic cosmology (CCC) is a cosmological model in the framework of general relativity, advanced by the theoretical physicists Roger Penrose and Vahe Gurzadyan.[1][2][3] In CCC, the universe iterates through infinite cycles, with the future timelike infinity of each previous iteration being identified with the Big Bang singularity of the next.[4]
CCC and the Fermi paradox In 2015 Gurzadyan and Penrose also discussed the Fermi paradox, the apparent contradiction between the lack of evidence but high probability estimates for the existence of extraterrestrial civilizations. Within conformal cyclic cosmology, the cosmic microwave background provides the possibility of information transfer from one aeon to another, including of intelligent signals within information panspermia concept.[12] 0712神も仏も名無しさん2018/07/22(日) 15:31:40.59ID:cn6pkcBn 来週のNHKSPは「アインシュタイン 消えた“天才脳”を追え」
One key challenge for inflation is the singularity problem. If inflation is realized by the dynamics of scalar matter fields coupled to Einstein gravity, then the HawkingPenrose singularity theorems [7] can be extended [8] to show that an inflationary universe is geodesically past incomplete. Thus, there necessarily is a singularity before the onset of inflation. Hence, the inflationary scenario cannot yield the complete history of the very early universe. A bouncing cosmological scenario naturally avoids this singularity problem, although at the cost of having to introduce new physics to obtain the bounce . 0734神も仏も名無しさん2018/07/25(水) 00:27:20.57ID:57l1gc9N 観測結果の問題から、ビッグバウンス理論も支持を集めている―この理論だって数十年後に消えている可能性もある
Jamie Seidel (7 December 2017). "Black hole at the dawn of time challenges our understanding of how the universe was formed". 9 December 2017.
It had reached its size just 690 million years after the point beyond which there is nothing. The most dominant scientific theory of recent years describes that point as the Big Bang — a spontaneous eruption of reality as we know it out of a quantum singularity. But another idea has recently been gaining weight: that the universe goes through periodic expansions and contractions — resulting in a “Big Bounce”. And the existence of early black holes has been predicted to be a key telltale as to whether or not the idea may be valid. This one is very big. To get to its size — 800 million times more mass than our Sun — it must have swallowed a lot of stuff.
....
As far as we understand it, the universe simply wasn’t old enough at that time to generate such a monster.
While most of the singularities of General Relativity are expected to be safely hidden behind event horizons by the cosmic censorship conjecture, we happen to live in the causal future of the classical big bang singularity, whose resolution constitutes the active field of early universe cosmology. Could the big bang be also hidden behind a causal horizon, making us immune to the decadent impacts of a naked singularity? We describe a braneworld description of cosmology with both 4d induced and 5d bulk gravity (otherwise known as Dvali-Gabadadze-Porati, or DGP model), which exhibits this feature: The universe emerges as a spherical 3-brane out of the formation of a 5d Schwarzschild black hole. In particular, we show that a pressure singularity of the holographic fluid, discovered earlier, happens inside the white hole horizon, and thus need not be real or imply any pathology. Furthermore, we outline a novel mechanism through which any thermal atmosphere for the brane, with comoving temperature of 20% of the 5D Planck mass can induce scale-invariant primordial curvature perturbations on the brane, circumventing the need for a separate process (such as cosmic inflation) to explain current cosmological observations. Finally, we note that 5D space-time is asymptotically flat, and thus potentially allows an S-matrix or (after minor modifications) AdS/CFT description of the cosmological big bang. 0747神も仏も名無しさん2018/07/25(水) 01:29:42.73ID:QDtQvsXG 論文を読みあさるのも結構だが、自分の見解はブログのまとめというのも困るな。 0748神も仏も名無しさん2018/07/25(水) 01:31:35.58ID:57l1gc9N>>747
One key challenge for inflation is the singularity problem. If inflation is realized by the dynamics of scalar matter fields coupled to Einstein gravity, then the HawkingPenrose singularity theorems [7] can be extended [8] to show that an inflationary universe is geodesically past incomplete. Thus, there necessarily is a singularity before the onset of inflation. Hence, the inflationary scenario cannot yield the complete history of the very early universe. A bouncing cosmological scenario naturally avoids this singularity problem, although at the cost of having to introduce new physics to obtain the bounce
Jamie Seidel (7 December 2017). "Black hole at the dawn of time challenges our understanding of how the universe was formed". 9 December 2017.
It had reached its size just 690 million years after the point beyond which there is nothing. The most dominant scientific theory of recent years describes that point as the Big Bang — a spontaneous eruption of reality as we know it out of a quantum singularity. But another idea has recently been gaining weight: that the universe goes through periodic expansions and contractions — resulting in a “Big Bounce”. And the existence of early black holes has been predicted to be a key telltale as to whether or not the idea may be valid. This one is very big. To get to its size — 800 million times more mass than our Sun — it must have swallowed a lot of stuff.
....
As far as we understand it, the universe simply wasn’t old enough at that time to generate such a monster.
The Return of the Phoenix Universe Jean-Luc Lehners, Paul J. Steinhardt, Neil Turok (Submitted on 5 Oct 2009) ttps://arxiv.org/abs/0910.0834 0771神も仏も名無しさん2018/07/27(金) 01:28:52.21ID:rx61+AHX>>730 有限には終わりがある。無限には無限の僕らが内包されている 0772神も仏も名無しさん2018/07/27(金) 01:44:52.62ID:ZRKKcNzu 自然災害ってすごいなあ。面白いなあと思います。地球の神秘ですよね。 いつまでも逃げず死亡者も多かったですしね。
