Universität zu Köln

Kiefer, Claus ORCID: 0000-0001-6163-9519 and Vardanyan, Tatevik (2022). Power spectrum for perturbations in an inflationary model for a closed universe. Gen. Relativ. Gravit., 54 (4). NEW YORK: SPRINGER/PLENUM PUBLISHERS. ISSN 1572-9532

Kiefer, Claus ORCID: 0000-0001-6163-9519 and Peter, Patrick ORCID: 0000-0002-7136-8326 (2022). Time in Quantum Cosmology. Universe, 8 (1). BASEL: MDPI. ISSN 2218-1997

Bouhmadi-López, Mariam, Kiefer, Claus ORCID: 0000-0001-6163-9519 and Martín-Moruno, Prado ORCID: 0000-0001-8073-4896 (2019). Phantom singularities and their quantum fate: general relativity and beyond—a CANTATA COST action topic. General Relativity and Gravitation, 51 (10). Springer. ISSN 0001-7701

Kiefer, Claus ORCID: 0000-0001-6163-9519 and Wichmann, David (2018). Semiclassical approximation of the Wheeler–DeWitt equation: arbitrary orders and the question of unitarity. General Relativity and Gravitation, 50 (6). Springer. ISSN 0001-7701

Kamenshchik, Alexander, Kiefer, Claus ORCID: 0000-0001-6163-9519 and Kwidzinski, Nick (2016). Classical and quantum cosmology of Born-Infeld type models. Phys. Rev. D, 93 (8). COLLEGE PK: AMER PHYSICAL SOC. ISSN 1550-2368

Albarran, Imanol ORCID: 0000-0003-4278-9372, Bouhmadi-Lopez, Mariam ORCID: 0000-0002-1529-1889, Kiefer, Claus ORCID: 0000-0001-6163-9519, Marto, Joao ORCID: 0000-0003-3974-9177 and Moniz, Paulo Vargas (2016). Classical and quantum cosmology of the little rip abrupt event. Phys. Rev. D, 94 (6). COLLEGE PK: AMER PHYSICAL SOC. ISSN 2470-0029

Brizuela, David, Kiefer, Claus ORCID: 0000-0001-6163-9519 and Kramer, Manuel ORCID: 0000-0002-4442-277X (2016). Quantum-gravitational effects on gauge-invariant scalar and tensor perturbations during inflation: The slow-roll approximation. Phys. Rev. D, 94 (12). COLLEGE PK: AMER PHYSICAL SOC. ISSN 2470-0029

Eingorn, Maxim, Kiefer, Claus ORCID: 0000-0001-6163-9519 and Zhuk, Alexander (2016). Scalar and vector perturbations in a universe with discrete and continuous matter sources. J. Cosmol. Astropart. Phys. (9). BRISTOL: IOP PUBLISHING LTD. ISSN 1475-7516

Eingorn, Maxim ORCID: 0000-0002-1545-7818 and Kiefer, Claus ORCID: 0000-0001-6163-9519 (2015). Scalar perturbations in cosmological models with dark energy-dark matter interaction. J. Cosmol. Astropart. Phys. (7). BRISTOL: IOP PUBLISHING LTD. ISSN 1475-7516

Kiefer, Claus ORCID: 0000-0001-6163-9519 (2014). Concept of Law in Physics On the Concept of Law in Physics. Eur. Rev., 22. S. S26 - 7. CAMBRIDGE: CAMBRIDGE UNIV PRESS. ISSN 1474-0575

Calcagni, Gianluca ORCID: 0000-0003-2631-4588, Kiefer, Claus ORCID: 0000-0001-6163-9519 and Steinwachs, Christian F. (2014). Quantum cosmological consistency condition for inflation. J. Cosmol. Astropart. Phys. (10). BRISTOL: IOP PUBLISHING LTD. ISSN 1475-7516

Bouhmadi-Lopez, Mariam ORCID: 0000-0002-1529-1889, Kiefer, Claus ORCID: 0000-0001-6163-9519 and Kraemer, Manuel (2014). Resolution of type IV singularities in quantum cosmology. Phys. Rev. D, 89 (6). COLLEGE PK: AMER PHYSICAL SOC. ISSN 1550-2368