pxf112

• CERN-TH-2018-065, IFUP-TH-2018
• e-Print: arXiv:1803.10242 [hep-ph] | PDF

Latham Boyle, Kieran Finn, Neil Turok

We propose that the state of the universe does {\it not} spontaneously violate CPT. Instead, the universe before the Big Bang is the CPT reflection of the universe after the bang. Phrased another way, the universe before the bang and the universe after the bang may be re-interpreted as a universe/anti-universe pair, created from nothing. CPT selects a unique vacuum state for the QFT on such a spacetime, which leads to a new perspective on the cosmological baryon asymmetry, and a new explanation for the observed dark matter abundance. In particular, if we assume that the matter fields in the universe are described by the standard model of particle physics (including right-handed neutrinos), we predict that one of the heavy neutrinos is stable, and that its density automatically matches the observed dark matter density if its mass is $4.8\times10^{8}~{\rm GeV}$. Among other predictions, we have: (i) that the three light neutrinos are majorana; (ii) that the lightest of these is exactly massless; and (iii) that there are no primordial long-wavelength gravitational waves. We mention connections to the strong CP problem and the arrow of time.

Lorenzo Calibbi, Robert Ziegler, Jure Zupan

We construct models with minimal field content that can simultaneously explain the muon g-2 anomaly and give the correct dark matter relic abundance. These models fall into two general classes, whether or not the new fields couple to the Higgs. For the general structure of models without new Higgs couplings, we provide analytical expressions that only depend on the $SU(2)_L$ representation. These results allow to demonstrate that only few models in this class can simultaneously explain $(g-2)_\mu$ and account for the relic abundance. The experimental constraints and perturbativity considerations exclude all such models, apart from a few fine-tuned regions in the parameter space, with new states in the few 100 GeV range. In the models with new Higgs couplings, the new states can be parametrically heavier by a factor $\sqrt{1/y_\mu}$, with $y_\mu$ the muon Yukawa coupling, resulting in masses for the new states in the TeV regime. At present these models are not well constrained experimentally, which we illustrate on two representative examples.

jxs1325

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Studies of galaxy surveys in the context of the cold dark matter paradigm have shown that the mass of the dark matter halo and the total stellar mass are coupled through a function that varies smoothly with mass. Their average ratio Mhalo/Mstars has a minimum of about 30 for galaxies with stellar masses near that of the Milky Way (approximately 5 × 1010 solar masses) and increases both towards lower masses and towards higher masses1,2. The scatter in this relation is not well known; it is generally thought to be less than a factor of two for massive galaxies but much larger for dwarf galaxies3,4. Here we report the radial velocities of ten luminous globular-cluster-like objects in the ultra-diffuse galaxy5 NGC1052–DF2, which has a stellar mass of approximately 2 × 108 solar masses. We infer that its velocity dispersion is less than 10.5 kilometres per second with 90 per cent confidence, and we determine from this that its total mass within a radius of 7.6 kiloparsecs is less than 3.4 × 108 solar masses. This implies that the ratio Mhalo/Mstars is of order unity (and consistent with zero), a factor of at least 400 lower than expected2. NGC1052–DF2 demonstrates that dark matter is not always coupled with baryonic matter on galactic scales.

Emanuele Castorina, Yu Feng, Uros Seljak, Francisco Villaescusa-Navarro

We develop a new method to constraint primordial non-Gaussianities of the local kind using unclustered tracers of the Large Scale Structure. We show that in the limit of low noise, zero bias tracers yield large improvement over standard methods, mostly due to vanishing sampling variance. We propose a simple technique to construct such a tracer, using environmental information obtained from the original sample, and validate our method with N-body simulations. Our results indicate that $\sigma_{f_{\mathrm{NL}}^{\mathrm{loc}}}\simeq1$ can be reached using only information on a single tracer of sufficiently high number density.