Kazuya Koyama Portrait

Professor Kazuya Koyama

Professor of Cosmology

Kazuya.Koyama@port.ac.uk

PhD Supervisor

View my research outputs
Faculty of Technology Cosmology and astrophysics Institute of Cosmology and Gravitation

Biography

I am a Professor of Cosmology in the Institute of Cosmology and Gravitation at the University of Portsmouth. My research interests lie in theoretical cosmology, particularly the origin of structure in our Universe and the late time acceleration of the Universe. My research is supported by the Science and Technology Facilities Council. I was supported by the European Research Council’s consolidator grant “Cosmological Tests of Gravity” between 2015 and 2021 and the European Research Council’s starting grant, “Modified gravity models as an alternative to dark energy” between 2008 and 2013. I was awarded my PhD from Kyoto University in 2002. Previous awards include RCUK academic fellowship, PPARC psotdoctoral fellowship, Japanese JSPS potdoctoral fellowship. In 2009 I was awarded the Philipe Leverhulme prize and in 2010 I received the Young Scientist Award of the Physical Society of Japan. I recieved the Yukawa-Kimura prize of the Yukawa memorial foundation in 2023. I was a PI of a Royal Society International Joint Project with the Yukawa Institute at Kyoto University. The collaboration between Portsmouth and Kyoto University was awarded the Daiwa-Adrian prize in 2010. 

Research interests

My main research interest lies in theoretical cosmology. I study the origin of structure in our Universe and test the early universe models using the statistical properties of the cosmic microwave background and the large scale structure of the Universe. I am also interested in explaining the late time acceleration of the Universe. Particularly I investigate a possibility to realise the late time acceleration by modifying general relativity on cosmological scales and develop cosmological tests of gravity.

 

Research outputs

2025

Forecasts for interacting dark energy with time-dependent momentum exchange

Cruickshank, N. J., Crittenden, R., Koyama, K., Bruni, M.

14 Oct 2025, In: Journal of Cosmology and Astroparticle Physics. 2025, 10, 25p., 052

Research output: Article

Dynamical Dark Energy in light of the DESI DR2 Baryonic Acoustic Oscillations Measurements

Gu, G., Wang, X., Wang, Y., Zhao, G., Pogosian, L., Koyama, K., Peacock, J. A., Cai, Z., Cervantes-Cota, J. L., Zhao, R., Ahlen, S., Bianchi, D., Brooks, D., Claybaugh, T., Cole, S., Macorra, A. d. l., de Mattia, A., Doel, P., Ferraro, S., Forero-Romero, J. E., Gaztañaga, E., Gontcho, S. G. A., Gutierrez, G., Hahn, C., Howlett, C., Ishak, M., Kehoe, R., Kirkby, D., Kneib, J., Lahav, O., Landriau, M., Guillou, L. L., Leauthaud, A., Levi, M., Manera, M., Meisner, A., Miquel, R., Moustakas, J., Muñoz-Gutiérrez, A., Nadathur, S., Newman, J. A., Palanque-Delabrouille, N., Percival, W., Prada, F., Pérez-Ràfols, I., Rossi, G., Samushia, L., Sanchez, E., Schlegel, D., Seo, H.

29 Sep 2025, In: Nature Astronomy

Research output: Article

A field-level reaction for screened modified gravity

Saadeh, D., Koyama, K., Morice-Atkinson, X.

22 Sep 2025, In: Monthly Notices of the Royal Astronomical Society

Research output: Article

Fast generation of weak lensing maps in modified gravity with COLA

Hoyland, S., Winther, H. A., Saadeh, D., Koyama, K., Izard, A.

1 Aug 2025, In: Monthly Notices of the Royal Astronomical Society. 541, 4, p. 3167–3183

Research output: Article

Euclid preparation LXXI. Simulations and nonlinearities beyond ΛCDM. 3. Constraints on f(R) models from the photometric primary probes

Collaboration, E., Koyama, K., Pamuk, S., Casas, S., Bose, B., Carrilho, P., Sáez-Casares, I., Atayde, L., Cataneo, M., Fiorini, B., Giocoli, C., Brun, A. M. C. L., Pace, F., Pourtsidou, A., Rasera, Y., Sakr, Z., Winther, H. -., Altamura, E., Adamek, J., Baldi, M., Breton, M. -., Rácz, G., Vernizzi, F., Amara, A., Andreon, S., Auricchio, N., Baccigalupi, C., Bardelli, S., Bernardeau, F., Bodendorf, C., Bonino, D., Branchini, E., Brescia, M., Brinchmann, J., Caillat, A., Camera, S., Capobianco, V., Carbone, C., Carretero, J., Duncan, C. A. J., Markovic, K., Percival, W. J., Sánchez, A. G., Taylor, A. N., Wang, Y., Weller, J., Gaztanaga, E., Joudaki, S., Kirkpatrick, C. C., Nadathur, S.

17 Jun 2025, In: Astronomy and Astrophysics. 698, 23p., A233

Research output: Article

A cosmological full-shape power spectra analysis using pre- and post-reconstructed density fields

Zhang, W., Zhao, R., Mu, X., Koyama, K., Takahashi, R., Wang, Y., Zhao, G.

28 May 2025, In: Research in Astronomy and Astrophysics. 25, 6, 11p., 065008

Research output: Article

Measuring the redshift-space distortions by cross-correlating the density fields before and after reconstruction

Zhang, W., Zhao, R., Mu, X., Koyama, K., Takahashi, R., Wang, Y., Zhao, G.

27 May 2025, In: The Astrophysical Journal. 985, 15p., 218

Research output: Article

Euclid. I. Overview of the Euclid mission

Collaboration, E., Mellier, Y., Barroso, J. A. A., Achúcarro, A., Adamek, J., Adam, R., Addison, G. E., Aghanim, N., Aguena, M., Ajani, V., Akrami, Y., Al-Bahlawan, A., Alavi, A., Albuquerque, I. S., Alestas, G., Alguero, G., Allaoui, A., Allevato, V., Alonso-Tetilla, A. V., Altieri, B., Alvarez-Candal, A., Amara, A., Avila, S., Bacon, D., Beutler, F., Bose, B., Collett, T. E., Fiorini, B., Fonseca, J., Gaztanaga, E., Joudaki, S., Koyama, K., Leclercq, F., Manera, M., Maraston, C., Markovic, K., Nadathur, S., Nichol, R. C., Noller, J., Pace, F., Pattison, C., Percival, W. J., Pollack, J. E., Pourtsidou, A., Raccanelli, A., Schewtschenko, J. A., Whalen, D. J., Winther, H. -., Youles, S., Fonseca De La Bella, L.

1 May 2025, In: Astronomy and Astrophysics. 697, 94p., A1

Research output: Article

Stochastic inflation beyond slow roll: noise modelling and importance sampling

Jackson, J. H. P., Assadullahi, H., Gow, A. D., Koyama, K., Vennin, V., Wands, D.

24 Apr 2025, In: Journal of Cosmology and Astroparticle Physics. 2025, 04, 30p., 073

Research output: Article

Euclid preparation: LXIII. Simulations and non-linearities beyond Lambda cold dark matter. 2. Results from non-standard simulations

Collaboration, E., Rácz, G., Breton, M. -., Fiorini, B., Brun, A. M. C. L., Winther, H. -., Sakr, Z., Pizzuti, L., Ragagnin, A., Gayoux, T., Altamura, E., Carella, E., Pardede, K., Verza, G., Koyama, K., Baldi, M., Pourtsidou, A., Vernizzi, F., Adame, A. G., Adamek, J., Avila, S., Carbone, C., Despali, G., Giocoli, C., Hernández-Aguayo, C., Hassani, F., Kunz, M., Li, B., Rasera, Y., Yepes, G., Gonzalez-Perez, V., Corasaniti, P. -., García-Bellido, J., Hamaus, N., Kiessling, A., Marinucci, M., Moretti, C., Mota, D. F., Piga, L., Pisani, A., Szapudi, I., Tallada-Crespí, P., Aghanim, N., Andreon, S., Baccigalupi, C., Casas, S., Markovic, K., Percival, W. J., Gaztanaga, E., Nadathur, S.

27 Mar 2025, In: Astronomy and Astrophysics. 695, 22p., A232

Research output: Article

View all my research outputs