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We comment on cases in the history of Astronomy, which may shed some light on the current established but enigmatic concordance model of Cosmology. Should the model be understood by adding new entities such as Dark Matter and Dark Energy, or by modifying the underlying theory? For example, the prediction and discovery of planet Neptune can be regarded as analogous to finding a dark component; while explaining the anomalous perihelion precession of Mercury by General Relativity can be taken as analogous to the possibility that modified gravity is an alternative to dark components of the universe. In this paper, we revise this analogy coming from the history of astronomy with an eye to illustrating some of the similarities and differences between the two cases.
We adopt in this work the idea that the building blocks of the visible Universe belong to a class of the irreducible representations of the Poincare group of transformations (the things) endowed with classificatory quantum numbers (the properties). A
Dark matter could emerge along with the Higgs as a composite pseudo-Nambu-Goldstone boson $chi$ with decay constant $fsim mathrm{TeV}$. This type of WIMP is especially compelling because its leading interaction with the Standard Model, the derivative
We consider cosmological models with a dynamical dark energy field, and study the presence of three types of commonly found instabilities, namely ghost (when fields have negative kinetic energy), gradient (negative momentum squared) and tachyon (nega
The LUX experimental group has just announced the most stringent upper limits so far obtained on the cross section of WIMP-nucleon elastic scattering [1]. This result is a factor of two to five below the previous best upper limit [2] and effectively
We consider dark matter (DM) with very weak couplings to the standard model (SM), such that its self-annihilation cross section is much smaller than the canonical one, $langlesigma vrangle_{chichi} ll 10^{-26}mathrm{cm}^3/mathrm{s}$. In this case DM