Gravity beyond Einstein? Part I: Physics and the Trouble with Experiments

2017 ◽  
Vol 72 (6) ◽  
pp. 493-525 ◽  
Author(s):  
Jochem Hauser ◽  
Walter Dröscher

AbstractThis article provides a review of the latest experimental results in quantum physics and astrophysics, discussing their repercussions on the advanced physical theories that go beyond both the SMs (standard models) of particle physics and cosmology. It will be shown that many of the essential concepts of the advanced theoretical models developed over the past 40 years are no longer tenable because they are contradicting the novel data. Most recent results (December 2016) from the Large Hadron Collider revealed no new matter particles up to particle masses of 1.6 TeV/c2, which is in accordance with recent ACME experimental data (2014) that saw no electric dipole moment for the electron as predicted by these theories. Moreover, the LUX experiment (since 2013) did not see any dark matter particles either, thus independently supporting LHC and ACME measurements. Furthermore, experimental particle physics seems to be telling us that dark matter particles (LHC results) do not exist, suggesting that dark matter particles either are more exotic or are more difficult to detect than had been predicted in the past decades (less likely with recent LHC results). Astrophysical observations since 1933, starting with Caltech astronomer Zwicky, however, have provided irrefutable evidence for the existence of dark matter, for instance, based on the phenomenon of gravitational lensing as well as observed rotational velocities of stars orbiting the galactic center that are deviating from Newton’s law. Surprisingly, recent astronomical observations by Bidin, ESO (2010, 2012, 2014), seem to indicate the absence of dark matter within galaxies. In addition, cosmology at present has no explanation for about 68 % of the energy in the Universe that comes in the form of dark energy. Recently, measured data from three entirely different types of experiments both on earth and in space (2006–2011) are hinting at completely novel features of gravity that, if confirmed, must be outside Einstein’s general relativity. Extreme gravitomagnetic and gravity-like fields may have been observed at cryogenic temperatures generated by a rotating ring or disk. However, these experimental results are not conclusive so far. The strength of these extreme fields has been calculated and, according to the respective equations, should be sufficient to serve as a basis for a gravitational technology that, for example, could establish long sought field propulsion (i.e. propulsion without fuel), actively researched by physicists and rocket engineers in the 1960s and 1990s. This article concludes with an outlook on the novel technology of gravitational engineering that might follow from gravity-like fields and discusses the novel physical concepts resulting from the existence of these extreme gravitomagnetic fields.

Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2406
Author(s):  
Spyros Argyropoulos ◽  
Oleg Brandt ◽  
Ulrich Haisch

Despite the fact that dark matter constitutes one of the cornerstones of the standard cosmological paradigm, its existence has so far only been inferred from astronomical observations, and its microscopic nature remains elusive. Theoretical arguments suggest that dark matter might be connected to the symmetry-breaking mechanism of the electroweak interactions or of other symmetries extending the Standard Model of particle physics. The resulting Higgs bosons, including the 125 GeV spin-0 particle discovered recently at the Large Hadron Collider, therefore represent a unique tool to search for dark matter candidates at collider experiments. This article reviews some of the relevant theoretical models as well as the results from the searches for dark matter in signatures that involve a Higgs-like particle at the Large Hadron Collider.


2018 ◽  
Vol 68 (1) ◽  
pp. 429-459 ◽  
Author(s):  
Antonio Boveia ◽  
Caterina Doglioni

Colliders, among the most successful tools of particle physics, have revealed much about matter. This review describes how colliders contribute to the search for particle dark matter, focusing on the highest-energy collider currently in operation, the Large Hadron Collider (LHC) at CERN. In the absence of hints about the character of interactions between dark matter and standard matter, this review emphasizes what could be observed in the near future, presents the main experimental challenges, and discusses how collider searches fit into the broader field of dark matter searches. Finally, it highlights a few areas to watch for the future LHC program.


2013 ◽  
Vol 53 (A) ◽  
pp. 528-533
Author(s):  
Giulio Auriemma

The most interesting cosmological open problems, baryon asymmetry, dark matter, inflation and dark energy, are not explained by the standard model of particle physics (SM). The final<br />goal of the Large Hadron Collider an experimental verification of the SM in the Higgs sector, and also a search for evidence of new physics beyond it. In this paper we will report some of the results obtained in 2010 and 2011, from the LHCb experiment dedicated to the study of CP violations and rare decays of heavy quarks.


2006 ◽  
Vol 3-4 ◽  
pp. 167-172 ◽  
Author(s):  
G. Pitarresi ◽  
A. Conti ◽  
U. Galietti

This work presents a set of experimental results based on the measured thermoelastic signal from GRP composite coupons adopting different lay-ups. A comparison is made with the thermoelastic signal predicted by two different analytical models: one based on the classical law of the thermoelastic effect for orthotropic materials, and the other based on a novel theory accounting for the presence of a resin layer on the external surface of the composite structure. The composite coupons were designed such to determine a significant difference in the predictions made by the two theoretical models. Experimental results have shown a far better match with the predictions based on the novel theory accounting for the presence of a surface resin rich layer.


2021 ◽  
Vol 59 (1) ◽  
pp. 247-289
Author(s):  
Lam Hui

We review the physics and phenomenology of wave dark matter: a bosonic dark matter candidate lighter than about 30 eV. Such particles have a de Broglie wavelength exceeding the average interparticle separation in a galaxy like the Milky Way and are, thus, well described as a set of classical waves. We outline the particle physics motivations for such particles, including the quantum chromodynamics axion as well as ultralight axion-like particles such as fuzzy dark matter. The wave nature of the dark matter implies a rich phenomenology: ▪  Wave interference gives rise to order unity density fluctuations on de Broglie scale in halos. One manifestation is vortices where the density vanishes and around which the velocity circulates. There is one vortex ring per de Broglie volume on average. ▪  For sufficiently low masses, soliton condensation occurs at centers of halos. The soliton oscillates and undergoes random walks, which is another manifestation of wave interference. The halo and subhalo abundance is expected to be suppressed at small masses, but the precise prediction from numerical wave simulations remains to be determined. ▪  For ultralight ∼10−22 eV dark matter, the wave interference substructures can be probed by tidal streams or gravitational lensing. The signal can be distinguished from that due to subhalos by the dependence on stream orbital radius or image separation. ▪  Axion detection experiments are sensitive to interference substructures for wave dark matter that is moderately light. The stochastic nature of the waves affects the interpretation of experimental constraints and motivates the measurement of correlation functions. Current constraints and open questions, covering detection experiments and cosmological, galactic, and black hole observations, are discussed.


2017 ◽  
Vol 45 ◽  
pp. 1760003 ◽  
Author(s):  
James G. O’Brien ◽  
Spasen Chaykov ◽  
Thomas L. Chiarelli ◽  
Taylor Saintable ◽  
Justin Harrington

Gravitational theories outside standard general relativity have been drawing increased attention over the past several years, mostly due to the lack of direct observational evidence of dark matter. With some recent very high level dark matter searches continuing, and the parameter space to search decreasing has lead to a new interest in rethinking gravity at the largest of scales. As an alternative gravitational theory, conformal gravity has enjoyed much of the success of Modified Newtonian Dynamics (MOND) in predicting phenomenology, but differs dramatically in its initial construction. In this work, we explore some recent advances in conformal gravity, which help to build the case for support of such an alternative theory. Here, we highlight conformal gravity’s success in fitting new rotation curves, its ability to explain velocity dispersions in clusters, the initial steps towards gravitational lensing and finally, some preliminary work on explaining universal centripetal acceleration trends in galaxies.


2014 ◽  
Vol 1 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Franco Giovannelli ◽  
Lola Sabau-Graziati

In this short review paper we comment on some the most important steps that have been made in the past decades for a better understanding of the physics governing our Universe. The results we discuss come from the many groundand-space-based experiments developed for measuring astrophysical sources in various energy bands. These experimental results are discussed within the framework of current theoretical models. Because of the limited length of this paper, we have selected only a few topics that, in our opinion, have been crucial for the progress of our understanding of the physics of cosmic sources.


2017 ◽  
Vol 26 (06) ◽  
pp. 1730012 ◽  
Author(s):  
Katherine Freese

Over the past few decades, a consensus picture has emerged in which roughly a quarter of the universe consists of dark matter. I begin with a review of the observational evidence for the existence of dark matter: rotation curves of galaxies, gravitational lensing measurements, hot gas in clusters, galaxy formation, primordial nucleosynthesis and Cosmic Microwave Background (CMB) observations. Then, I discuss a number of anomalous signals in a variety of data sets that may point to discovery, though all of them are controversial. The annual modulation in the DAMA detector and/or the gamma-ray excess seen in the Fermi Gamma Ray Space Telescope from the Galactic Center could be due to WIMPs; a 3.5 keV X-ray line from multiple sources could be due to sterile neutrinos; or the 511 keV line in INTEGRAL data could be due to MeV dark matter. All of these would require further confirmation in other experiments or data sets to be proven correct. In addition, a new line of research on dark stars is presented, which suggests that the first stars to exist in the universe were powered by dark matter heating rather than by fusion: the observational possibility of discovering dark matter in this way is discussed.


2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Katherine Fraser ◽  
Aditya Parikh ◽  
Weishuang Linda Xu

Abstract A statistically significant excess of gamma rays has been reported and robustly confirmed in the Galactic Center over the past decade. Large local dark matter densities suggest that this Galactic Center Excess (GCE) may be attributable to new physics, and indeed it has been shown that this signal is well-modelled by annihilations dominantly into $$ b\overline{b} $$ b b ¯ with a WIMP-scale cross section. In this paper, we consider Majorana dark matter annihilating through a Higgs portal as a candidate source for this signal, where a large CP-violation in the Higgs coupling may serve to severely suppress scattering rates. In particular, we explore the phenomenology of two UV completions, a singlet-doublet model and a doublet-triplet model, and map out the available parameter space which can give a viable signal while respecting current experimental constraints.


Author(s):  
John Ellis

The Standard Model of particle physics agrees very well with experiment, but many important questions remain unanswered, among them are the following. What is the origin of particle masses and are they due to a Higgs boson? How does one understand the number of species of matter particles and how do they mix? What is the origin of the difference between matter and antimatter, and is it related to the origin of the matter in the Universe? What is the nature of the astrophysical dark matter? How does one unify the fundamental interactions? How does one quantize gravity? In this article, I introduce these questions and discuss how they may be addressed by experiments at the Large Hadron Collider, with particular attention to the search for the Higgs boson and supersymmetry.


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