Dear Colleagues,

The various approaches toward quantum gravity mainly concern the description of the Planck and/or trans-Planckian energy regime. The UV completion of all the fields, including the gravitational one, is the ultimate target of such theories. However, experiments at such energies will never be performed and even if in future there is to be a favorite model/Lagrangian with an associated mathematical machinery for calculating physical quantities/measurables in a meaningful way, this is not enough. It is expected that one can always construct an alternative model (close or not close to the hypothetical successful one) which may also be acceptable/successful in the UV regime where experiments are absent and only avoidance of loop infinities and/or of spacetime singularities is required.

A possible way out of this loss of feedback is to study the IR quantum gravity phenomenology. The aim is to examine if IR corrections are significant enough to be tested by some kind of experiment or by recent or future cosmological or astrophysical observations. The energy scale of IR corrections can include the far infrared regime or intermediate IR energy scales. Another interesting, related issue is the Cohen–Kaplan–Nelson idea of interconnecting IR and UV scales; this conjecture and related ideas may shed light to the problem. Furthermore, a deep understanding of IR analysis is unavoidably connected with solving the mystery of the passage from the quantum to the classical regime. Recently, very interesting discussions appeared in the literature about the asymptotic safety program and perturbative effective field theory approaches to IR corrections. We welcome further constructive criticism about alternative ways to estimate IR gravity corrections and their phenomenological implications.

We invite colleagues to submit contributions to this Special Issue on “IR Quantum Gravity, Theoretical Challenges, and Cosmological/Astrophysical Consequences” of the journal Universe, addressing both theoretical and phenomenological aspects concerning:

• IR quantum gravity and non-perturbative functional renormalization group flow;
• IR perturbative corrections to the gravity sector;
• IR and UV scale interconnection;
• IR corrections and cosmological consequences, inflation, large scale structure, dark energy, etc.;
• IR corrections and astrophysical consequences, black holes, supernovae, galactic rotational curves, etc.;
• IR corrections to the gravity sector and gravitational waves;
• UV to IR passage and explanation of decoherence, physical interpretation of the “collapse of the wave function”.

Prof. Dr. Vasilios Zarikas
Prof. Dr. Pantelis S. Apostolopoulos
Guest Editors

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