Signatures of extra dimensions in gravitational waves David Andriot, Gustavo Lucena Gómez (Submitted on 24 Apr 2017) Considering gravitational waves propagating on the most general 4+N-dimensional space-time, we investigate the effects due to the N extra dimensions on the four-dimensional waves. All wave equations are derived in general and discussed. On Minkowski4 times an arbitrary Ricci-flat compact manifold, we find: a massless wave with an additional polarization, the breathing mode, and extra waves with high frequencies fixed by Kaluza-Klein masses. We discuss whether these two effects could be observed. Comments: 21 pages + appendices, comments welcome! Subjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph) Cite as: arXiv:1704.07392 [hep-th] (or arXiv:1704.07392v1 [hep-th] for this version) Any evaluation of this proposal? GR in 4 D has one prediction and non observation of additional polarization implies GR in 4D is correct, no extra dimensions. In string theory, are the extra 6 spatial dimenions considered frozen, immutable for all eternity, while the 3 large spatial dimensions can curve as described by Einstein? Were those extra 6 dimensions frozen from the very beginning of time or does string theory state the universe start out as 10 flat dimensions then at some time 6 became compactified and 3 remain large and 1 became time?