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We propose using fuzzy axion dark matter to test the anthropic principle. A very light axion can be directly detectable, at least by black hole superradiance effects. The idea then is that gravitational and astrophysical observations can discover a light axion in the regime where it must be all of dark matter with abundance which must be set up by the anthropic principle, due to excessive primordial misalignment induced by inflation-induced Brownian drift of fluctuations. Yet it may turn out that dark matter is something else instead of this axion. Since the de Sitter-induced axion misalignment controlled only by the de Sitter curvature cannot be evaded, this would invalidate the anthropic prediction of the dark matter abundance.
Recently the multitude of vacua in string theory have led some authors to advocate the anthropic principle as a possible resolution for the contrived set of parameters that seem to govern our universe. I suggest that string theories should be viewed as effective theories, and hence of limited utility rather than as ``theories of everything''. I propose that quantum gravity should admit a form of determinism and that the self-dual points under phase-space duality should play a prominent role in the vacuum selection principle.
Results of recent experiment reinstate feasibility to the hypothesis that biomolecular homochirality originates from beta decay. Coupled with hints that this process occurred extraterrestrially suggests aluminum-26 as the most likely source. If true, then its appropriateness is highly dependent on the half-life and energy of this decay. Demanding that this mechanism hold places new constraints on the anthropically allowed range for multiple parameters, including the electron mass, difference between up and down quark masses, the fine structure constant, and the electroweak scale. These new constraints on particle masses are tighter than those previously found. However, one edge of the allowed region is nearly degenerate with an existing bound, which, using what is termed here as `the principle of noncoincident peril', is argued to be a strong indicator that the fine structure constant must be an environmental parameter in the multiverse.
We re-examine claims that anthropic arguments provide an explanation for the observed smallness of the cosmological constant, and argue that correlations between the cosmological constant value and the existence of life can be demonstrated only under restrictive assumptions. Causal effects are more subtle to uncover.
The relaxion mechanism provides a potentially elegant solution to the hierarchy problem without resorting to anthropic or other fine-tuning arguments. This mechanism introduces an axion-like field, dubbed the relaxion, whose expectation value determines the electroweak hierarchy as well as the QCD strong CP violating $\barθ$ parameter. During an inflationary period, the Higgs mass squared is selected to be negative and hierarchically small in a theory which is consistent with 't Hooft's technical naturalness criteria. However, in the original model proposed by Graham, Kaplan and Rajendran (2015), the relaxion does not solve the strong CP problem, and in fact contributes to it, as the coupling of the relaxion to the Higgs field and the introduction of a linear potential for the relaxion produces large strong CP violation. We resolve this tension by considering inflation with a Hubble scale which is above the QCD scale but below the weak scale, and estimating the Hubble temperature dependence of the axion mass. The relaxion potential is thus very different during inflation than it is today. We find that provided the inflationary Hubble scale is between the weak scale and about 3 GeV,
The definition of thermodynamic entropy is dependent on one's assignment of physical microstates to observed macrostates. As a result, low entropy in the distant past could be equivalently explained by selection of a particular observer. In this paper, I make the case that because we observe a low-entropy past everywhere even as we look further and further away, anthropic selection over observers does not explain the non-equilibrium state of the observed cosmos. Under a uniform prior over possible world states, the probability of a non-equilibrium past, given our local observations, decreases to zero as the size of the world tends toward infinity. This claim is not dependent on choice of observer, unless the amount of information used to encode the observer's coarse-graining perception function scales linearly with the size of the world. As a result, for anthropic selection to choose a world like the one we live in, the initial state of a universe with size $N$ must be low-information, having Kolmogorov complexity that does not scale with $N$.
The anthropic principle implies that life can emerge and be sustained only in a narrow range of values of fundamental constants. Here we show that anthropic arguments can set powerful constraints on {\em transient} variations of the fine-structure constant $α$ over the past 4 billion years since the appearance of lifeforms on Earth. We argue that the passage through Earth of a macroscopic dark matter clump with a value of $α$ inside differing substantially from its nominal value would make Earth uninhabitable. We demonstrate that in the regime of extreme variation of $α$, the periodic table of elements is truncated, water fails to serve as a universal solvent, and protons become unstable. Thereby, the anthropic principle constrains the likelihood of such encounters on a 4-billion-year timescale. This enables us to improve existing astrophysical bounds on certain dark matter model couplings by several orders of magnitude.
The anthropic explanation for the peculiarly small observed value of the cosmological constant $Λ_{\rm obs}$ argues that this value promotes the formation of stars, planets, and ultimately of observers such as ourselves. I show that a recent analytic model of cosmic star formation predicts that although $Λ_{\rm obs}$ maximises the overall efficiency of star formation in the universe, the probability of generating observers peaks at $\sim400-500 \, Λ_{\rm obs}$. These preliminary results suggest that an immediate connection between star formation efficiency and observers' generation is not straightforward, and highlight the subtleties involved with the application of anthropic reasoning.
The Anthropic Principle has been with us since the 1970s. This Principle is advanced to account for the "fine tuning" of the 25 constants of the Standard Model of Particle Physics. Were these constants very different, life could not exist. The Anthropic Principle conditions on the existence of life and concludes that the value of the 25 constants must be within a range that allows life. The most common further step is to postulate the existence of a vast multiverse with vastly many combinations of the values of the 25 constants. By conditioning on our own life, we must be in a universe whose values allow life. The Anthropic Principle is commonly held to be untestable because we cannot be in contact with other universes. I aim here to show the Anthropic Principle is testable and that its explanatory power is weak: The Principle seems to make testably false predictions about planet Earth and the life on it. The Anthropic Principle seems unable to predict the existence of 98 stable atoms, when only 19 small atoms are needed for life.
I review the role and meaning of the Anthropic Principle, particularly in its relevance to particle physics.
The anthropic principle is an inevitable constraint on the space of possible theories. As such it is central to determining the limits of physics. In particular, we contend that what is ultimately possible in physics is determined by restrictions on the computational capacity of the universe, and that observers are more likely to be found where more complicated calculations are possible. Our discussion covers the inevitability of theoretical bias and how anthropics and computation can be an aid to imposing these biases on the theory landscape in a systematic way. Further, we argue for (as far as possible) top-down rather than bottom-up anthropic measures, contending that that the latter can often be misleading. We begin the construction of an explicit computational measure by examining the effect of the cosmological constant on computational bounds in a given universe, drawing from previous work on using entropy production as a proxy for observers by Bousso, Harnik, Kribs and Perez. In addition, we highlight a few of the additional computational considerations that may be used to extend such a measure.
NASA’s upgraded Cold Atom Lab is turning the International Space Station into a frontier for quantum research, creating ultra-cold matter that behaves in astonishing ways。 The experiments could unlock new discoveries about the universe while paving the way for powerful future technologies in space and on Earth
What if some black holes aren’t black holes at all。 A new theoretical study suggests that when a massive star collapses, it might not form a singularity hidden behind an event horizon。 Instead, the collapse could trigger the birth of a tiny new universe inside the dying star
Join us on the livestream at 1 pm ET and ask questions about the aftermath of New Glenn
A new study suggests Earth may have been sending tiny hitchhikers to Venus for billions of years。 Researchers found that asteroid impacts could launch microbes into space, where some might survive the journey and end up suspended in Venus' clouds。 If future missions detect life there, there's a surprising chance it didn't originate on Venus at all—
His doctors went looking for cancer, then they saw the worms' heads
Move would test whether group can turn ambition into a mass-market phone business
SETI scientists searched the interstellar object 3I/ATLAS for radio signals that could indicate extraterrestrial technology but found nothing beyond human-made interference。 Even so, the rapid-response observations helped confirm the object's natural origin and showcased how future interstellar visitors can be investigated for signs of intelligent
Researchers discovered that hydrogen radicals generated by intense UV light can break down stubborn PFAS “forever chemicals” without added chemicals。 The breakthrough reveals a key mechanism that could lead to greener and more effective technologies for permanently destroying these pollutants
Clicking on the links now reveals blank pages and empty PDFs。 "Intellectually, it’s not acceptable