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Department of Applied Mathematics and Theoretical Physics

Dr Toshiya Namikawa

Career

  • 2019 - Now : Senior Research Associate, DAMTP, University of Cambridge
  • 2018 - 2018: Assistant Researcher (termed Assistant Professor), National Taiwan Univeristy
  • 2014 - 2017: Postdoctoral Researcher (with JSPS fellowship for two years), KIPAC, Stanford University
  • 2013 - 2014: Postdoctoral Researcher, Yukawa Institute for Theoretical Physics, Kyoto University
  • 2010 - 2013: PhD Student, University of Tokyo
  • 2008 - 2010: Master Student, University of Tokyo

Research

Toshiya is a member of the Department of Applied Mathematics and Theoretical Physics, in the Relativity and Gravitation research group. He is working on data-driven cosmology, the intersection between theoretical and observational cosmology. His current interests include B-mode analysis, gravitational lensing of CMB, cosmic birefringence, reionization and non-Gaussianity. He is an active member of several CMB experiments. 

 

Selected Publications

  • T. Namikawa et al. (ACTPol Collaboration), "The Atacama Cosmology Telescope: Constraints on Cosmic Birefringence", Phys. Rev. D, 101, 10465, 2020, arXiv:2001.10465
  • T. Namikawa et al. (POLARBEAR and Subaru-HSC Collaborations), "Evidence for the Cross-correlation between Cosmic Microwave Background Polarization Lensing from POLARBEAR and Cosmic Shear from Subaru Hyper Suprime-Cam", Astrophys. J., 882, 12, 2019, arXiv:1904.02116
  • BICEP2/Keck Array Collaborations, "BICEP2 / Keck Array X: Improved Constraints on Inflationary Gravitational Waves using BICEP2/Keck Data up to the 2015 Season in Conjunction with WMAP/Planck", Phys. Rev. Lett., 121, 221301, 2018, arXiv:1810.05216
  • T. Namikawa, "CMB internal delensing with general optimal estimator for higher-order correlations", Phys. Rev. D, 95, 103514, 2017, arXiv:1703.00169
  • BICEP2/Keck Array Collaborations, "BICEP2 / Keck Array IX: New Bounds on Anisotropies of CMB Polarization Rotation and Implications for Axion-Like Particles and Primordial Magnetic Fields", Phys. Rev. D, 96, 102003, 2017, arXiv:1705.02523
  • BICEP2/Keck Array Collaborations, "BICEP2 / Keck Array VIII: Measurement of Gravitational Lensing from Large-Scale B-mode Polarization", Astrophys. J., 833, 228, 2016, arXiv:1606.01968
  • T. Namikawa, "CMB Lensing bispectrum from Nonlinear Growth of the Large Scale Structure", Phys. Rev. D Rapid Communications, 93, 121301, 2016, arXiv:1604.08578
  • T. Namikawa et al., "Anisotropies of gravitational-wave standard sirens as a new cosmological probe without redshift information", Phys. Rev. Lett., 116, 0121302, 2016, arXiv:1511.04638
  • T. Namikawa et al.. "Bias-Hardened CMB Lensing", Mon. Not. R. Astron. Soc., 431, 609, 2013, arXiv:1209.0091
  • T. Namikawa et al., "Full-sky lensing reconstruction of gradient and curl modes from CMB maps", J. Cosmol. Astropart. Phys., 01, 007, 2012, arXiv:1110.1718

Publications

Requirements on the gain calibration for LiteBIRD polarisation data with blind component separation
F Carralot, A Carones, N Krachmalnicoff, T Ghigna, A Novelli, L Pagano, F Piacentini, C Baccigalupi, D Adak, A Anand, J Aumont, S Azzoni, M Ballardini, AJ Banday, RB Barreiro, N Bartolo, S Basak, A Basyrov, M Bersanelli, M Bortolami, T Brinckmann, F Cacciotti, P Campeti, E Carinos, FJ Casas, K Cheung, L Clermont, F Columbro, G Conenna, G Coppi, A Coppolecchia, F Cuttaia, P de Bernardis, M De Lucia, S Della Torre, E Di Giorgi, P Diego-Palazuelos, T Essinger-Hileman, E Ferreira, F Finelli, C Franceschet, G Galloni, M Galloway, M Gervasi, RT Génova-Santos, S Giardiello, C Gimeno-Amo, E Gjerlow, A Gruppuso, M Hazumi, S Henrot-Versillé, LT Hergt, E Hivon, H Ishino, B Jost, K Kohri, L Lamagna, C Leloup, M Lembo, F Levrier, AI Lonappan, M López-Caniego, G Luzzi, J Macias-Perez, E Martinez-González, S Masi, S Matarrese, T Matsumura, S Micheli, M Monelli, L Montier, G Morgante, B Mot, L Mousset, Y Nagano, R Nagata, T Namikawa, P Natoli, I Obata, A Occhiuzzi, A Paiella, D Paoletti, G Pascual-Cisneros, G Patanchon, V Pavlidou, G Pisano, G Polenta, L Porcelli, G Puglisi, N Raffuzzi, M Remazeilles, JA Rubino-Martin, M Ruiz-Granda, J Sanghavi, D Scott, M Shiraishi, RM Sullivan, Y Takase, K Tassis, L Terenzi
– Journal of Cosmology and Astroparticle Physics
(2025)
2025,
019
(doi: 10.1088/1475-7516/2025/01/019)
Tomographic constraint on anisotropic cosmic birefringence
T Namikawa
– Physical Review D
(2025)
111,
023501
(doi: 10.1103/physrevd.111.023501)
Multi-dimensional optimisation of the scanning strategy for the LiteBIRD space mission
Y Takase, L Vacher, H Ishino, G Patanchon, L Montier, SL Stever, K Ishizaka, Y Nagano, W Wang, J Aumont, K Aizawa, A Anand, C Baccigalupi, M Ballardini, AJ Banday, RB Barreiro, N Bartolo, S Basak, M Bersanelli, M Bortolami, T Brinckmann, E Calabrese, P Campeti, E Carinos, A Carones, FJ Casas, K Cheung, L Clermont, F Columbro, A Coppolecchia, F Cuttaia, G D'Alessandro, P de Bernardis, T de Haan, E de la Hoz, S Della Torre, P Diego-Palazuelos, HK Eriksen, J Errard, F Finelli, U Fuskeland, G Galloni, M Galloway, M Gervasi, T Ghigna, S Giardiello, C Gimeno-Amo, E Gjerløw, R González González, A Gruppuso, M Hazumi, S Henrot-Versillé, LT Hergt, K Ikuma, K Kohri, L Lamagna, M Lattanzi, C Leloup, M Lembo, F Levrier, AI Lonappan, M López-Caniego, G Luzzi, B Maffei, E Martínez-González, S Masi, S Matarrese, FT Matsuda, T Matsumura, S Micheli, M Migliaccio, M Monelli, G Morgante, B Mot, R Nagata, T Namikawa, A Novelli, K Odagiri, S Oguri, R Omae, L Pagano, D Paoletti, F Piacentini, M Pinchera, G Polenta, L Porcelli, N Raffuzzi, M Remazeilles, A Ritacco, M Ruiz-Granda, Y Sakurai, D Scott, Y Sekimoto, M Shiraishi, G Signorelli, RM Sullivan, H Takakura, L Terenzi, M Tomasi, M Tristram
– Journal of Cosmology and Astroparticle Physics
(2024)
2024,
036
(doi: 10.1088/1475-7516/2024/12/036)
LiteBIRD science goals and forecasts. Mapping the hot gas in the Universe
M Remazeilles, M Douspis, JA Rubiño-Martín, AJ Banday, J Chluba, P de Bernardis, M De Petris, C Hernández-Monteagudo, G Luzzi, J Macias-Perez, S Masi, T Namikawa, L Salvati, H Tanimura, K Aizawa, A Anand, J Aumont, C Baccigalupi, M Ballardini, RB Barreiro, N Bartolo, S Basak, M Bersanelli, D Blinov, M Bortolami, T Brinckmann, E Calabrese, P Campeti, E Carinos, A Carones, FJ Casas, K Cheung, L Clermont, F Columbro, A Coppolecchia, F Cuttaia, T de Haan, E de la Hoz, S Della Torre, P Diego-Palazuelos, G D'Alessandro, HK Eriksen, F Finelli, U Fuskeland, G Galloni, M Galloway, M Gervasi, RT Génova-Santos, T Ghigna, S Giardiello, C Gimeno-Amo, E Gjerløw, R González González, A Gruppuso, M Hazumi, S Henrot-Versillé, LT Hergt, D Herranz, K Kohri, E Komatsu, L Lamagna, M Lattanzi, C Leloup, F Levrier, AI Lonappan, M López-Caniego, B Maffei, E Martínez-González, S Matarrese, T Matsumura, S Micheli, M Migliaccio, M Monelli, L Montier, G Morgante, Y Nagano, R Nagata, A Novelli, R Omae, L Pagano, D Paoletti, V Pavlidou, F Piacentini, M Pinchera, G Polenta, L Porcelli, A Ritacco, M Ruiz-Granda, Y Sakurai, D Scott, M Shiraishi, SL Stever, RM Sullivan, Y Takase, K Tassis, L Terenzi, M Tomasi, M Tristram, L Vacher, B van Tent
– Journal of Cosmology and Astroparticle Physics
(2024)
2024,
026
(doi: 10.1088/1475-7516/2024/12/026)
Constraining ultralight ALP dark matter in light of cosmic birefringence
D Zhang, EGM Ferreira, I Obata, T Namikawa
– Physical Review D
(2024)
110,
103525
(doi: 10.1103/PhysRevD.110.103525)
Efficient estimation of rotation-induced bias to reconstructed CMB lensing power spectrum
H Cai, Y Guan, T Namikawa, A Kosowsky
– Physical Review D
(2024)
110,
103507
(doi: 10.1103/physrevd.110.103507)
Tomographic constraint on anisotropic cosmic birefringence
T Namikawa
(2024)
(link to publication)
The Simons Observatory: Combining cross-spectral foreground cleaning with multitracer B-mode delensing for improved constraints on inflation
E Hertig, K Wolz, T Namikawa, AB Lizancos, S Azzoni, I Abril-Cabezas, D Alonso, C Baccigalupi, E Calabrese, A Challinor, J Errard, G Fabbian, C Hervías-Caimapo, B Jost, N Krachmalnicoff, AI Lonappan, M Morshed, L Pagano, B Sherwin
– Physical Review D
(2024)
110,
043532
(doi: 10.1103/PhysRevD.110.043532)
Efficient estimation of rotation-induced bias to reconstructed CMB lensing power spectrum
H Cai, Y Guan, T Namikawa, A Kosowsky
(2024)
(link to publication)
Constraining Ultralight ALP Dark Matter in Light of Cosmic Birefringence
D Zhang, EGM Ferreira, I Obata, T Namikawa
(2024)
(link to publication)
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Research Group

Relativity and Gravitation

Email

tn334@damtp.cam.ac.uk

Room

B1.09

Telephone

01223 337843

Study at Cambridge

About the University

Research at Cambridge