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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

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)
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)
LiteBIRD science goals and forecasts: primordial magnetic fields
D Paoletti, JA Rubino-Martin, M Shiraishi, D Molinari, J Chluba, F Finelli, C Baccigalupi, J Errard, A Gruppuso, AI Lonappan, A Tartari, E Allys, A Anand, J Aumont, M Ballardini, AJ Banday, RB Barreiro, N Bartolo, M Bersanelli, M Bortolami, T Brinckmann, E Calabrese, P Campeti, A Carones, FJ Casas, K Cheung, L Clermont, F Columbro, G Conenna, A Coppolecchia, F Cuttaia, G D’Alessandro, P de Bernardis, S Della Torre, P Diego-Palazuelos, HK Eriksen, U Fuskeland, G Galloni, M Galloway, M Gerbino, M Gervasi, T Ghigna, S Giardiello, C Gimeno-Amo, E Gjerløw, F Grupp, M Hazumi, S Henrot-Versillé, LT Hergt, E Hivon, K Ichiki, H Ishino, K Kohri, E Komatsu, N Krachmalnicoff, L Lamagna, M Lattanzi, M Lembo, F Levrier, M López-Caniego, G Luzzi, E Martínez-González, S Masi, S Matarrese, S Micheli, M Migliaccio, M Monelli, L Montier, G Morgante, L Mousset, R Nagata, T Namikawa, P Natoli, A Novelli, I Obata, A Occhiuzzi, K Odagiri, L Pagano, A Paiella, G Pascual-Cisneros, F Piacentini, G Piccirilli, M Remazeilles, A Ritacco, M Ruiz-Granda, Y Sakurai, D Scott, SL Stever, RM Sullivan, Y Takase, K Tassis, L Terenzi, M Tristram, L Vacher, B van Tent, P Vielva, IK Wehus, G Weymann-Despres, M Zannoni, Y Zhou
– Journal of Cosmology and Astroparticle Physics
(2024)
2024,
086
(doi: 10.1088/1475-7516/2024/07/086)
Systematic Effects on Lensing Reconstruction from a Patchwork of CMB Polarization Maps
R Nagata, T Namikawa
– Progress of Theoretical and Experimental Physics
(2024)
2024,
083e01
(doi: 10.1093/ptep/ptae117)
The Atacama Cosmology Telescope: Reionization kSZ trispectrum methodology and limits
N MacCrann, FJ Qu, T Namikawa, B Bolliet, H Cai, E Calabrese, SK Choi, W Coulton, O Darwish, S Ferraro, Y Guan, JC Hill, M Hilton, R Hlozek, D Kramer, MS Madhavacheril, K Moodley, N Sehgal, BD Sherwin, C Sifón, ST Staggs, H Trac, A Van Engelen, EM Vavagiakis
– Monthly Notices of the Royal Astronomical Society
(2024)
532,
4247
(doi: 10.1093/mnras/stae1746)
Exact CMB B-mode power spectrum from anisotropic cosmic birefringence
T Namikawa
– Physical Review D
(2024)
109,
123521
(doi: 10.1103/PhysRevD.109.123521)
Impact of beam far side-lobe knowledge in the presence of foregrounds for LiteBIRD
C Leloup, G Patanchon, J Errard, C Franceschet, JE Gudmundsson, S Henrot-Versillé, H Imada, H Ishino, T Matsumura, G Puglisi, W Wang, A Adler, J Aumont, R Aurlien, C Baccigalupi, M Ballardini, AJ Banday, RB Barreiro, N Bartolo, A Basyrov, M Bersanelli, D Blinov, M Bortolami, T Brinckmann, P Campeti, A Carones, F Carralot, FJ Casas, K Cheung, L Clermont, F Columbro, G Conenna, A Coppolecchia, F Cuttaia, N Dachlythra, G D'Alessandro, P de Bernardis, T de Haan, M De Petris, S Della Torre, P Diego-Palazuelos, HK Eriksen, F Finelli, U Fuskeland, G Galloni, M Galloway, M Georges, M Gerbino, M Gervasi, RT Génova-Santos, T Ghigna, S Giardiello, C Gimeno-Amo, E Gjerløw, A Gruppuso, M Hazumi, LT Hergt, D Herranz, E Hivon, TD Hoang, B Jost, K Kohri, N Krachmalnicoff, AT Lee, M Lembo, F Levrier, AI Lonappan, M López-Caniego, J Macias-Perez, E Martínez-González, S Masi, S Matarrese, S Micheli, M Monelli, L Montier, G Morgante, B Mot, L Mousset, T Namikawa, P Natoli, A Novelli, F Noviello, I Obata, K Odagiri, L Pagano, A Paiella, D Paoletti, G Pascual-Cisneros, V Pavlidou, F Piacentini, G Piccirilli, G Pisano, G Poleta, N Raffuzzi, M Remazeilles, A Ritacco, A Rizzieri, M Ruiz-Granda, Y Sakurai, M Shiraishi
– Journal of Cosmology and Astroparticle Physics
(2024)
2024,
011
(doi: 10.1088/1475-7516/2024/06/011)
LiteBIRD science goals and forecasts: improving sensitivity to inflationary gravitational waves with multitracer delensing
T Namikawa, A Lonappan, C Baccigalupi, N Bartolo, D Beck, K Benabed, A Challinor, P Diego-Palazuelos, J Errard, S Farrens, A Gruppuso, N Krachmalnicoff, M Migliaccio, E Martínez-González, V Pettorino, G Piccirilli, M Ruiz-Granda, B Sherwin, J Starck, P Vielva, R Akizawa, A Anand, J Aumont, R Aurlien, S Azzoni, M Ballardini, A Banday, R Barreiro, M Bersanelli, D Blinov, M Bortolami, T Brinckmann, E Calabrese, P Campeti, A Carones, F Carralot, F Casas, K Cheung, L Clermont, F Columbro, G Conenna, A Coppolecchia, F Cuttaia, G D'Alessandro, P de Bernardis, T de Haan, M De Petris, S Della Torre, E Di Giorgi, H Eriksen, F Finelli, C Franceschet, U Fuskeland, G Galloni, M Galloway, M Georges, M Gerbino, M Gervasi, T Ghigna, S Giardiello, C Gimeno-Amo, E Gjerløw, M Hazumi, S Henrot-Versillé, L Hergt, E Hivon, K Kohri, E Komatsu, L Lamagna, M Lattanzi, C Leloup, M Lembo, M López-Caniego, G Luzzi, B Maffei, S Masi, M Massa, S Matarrese, T Matsumura, S Micheli, A Moggi, M Monelli, L Montier, G Morgante, B Mot, L Mousset, R Nagata, P Natoli, A Novelli, I Obata, A Occhiuzzi, L Pagano, A Paiella, D Paoletti, G Pascual-Cisneros, V Pavlidou, F Piacentini, M Pinchera, G Pisano, G Polenta
– Journal of Cosmology and Astroparticle Physics
(2024)
2024,
010
(doi: 10.1088/1475-7516/2024/06/010)
LiteBIRD science goals and forecasts: a full-sky measurement of gravitational lensing of the CMB
AI Lonappan, T Namikawa, G Piccirilli, P Diego-Palazuelos, M Ruiz-Granda, M Migliaccio, C Baccigalupi, N Bartolo, D Beck, K Benabed, A Challinor, J Errard, S Farrens, A Gruppuso, N Krachmalnicoff, E Martínez-González, V Pettorino, B Sherwin, J Starck, P Vielva, R Akizawa, A Anand, J Aumont, R Aurlien, S Azzoni, M Ballardini, AJ Banday, RB Barreiro, M Bersanelli, D Blinov, M Bortolami, T Brinckmann, E Calabrese, P Campeti, A Carones, F Carralot, FJ Casas, K Cheung, L Clermont, F Columbro, G Conenna, A Coppolecchia, F Cuttaia, G D'Alessandro, P de Bernardis, M De Petris, S Della Torre, E Di Giorgi, HK Eriksen, F Finelli, C Franceschet, U Fuskeland, G Galloni, M Galloway, M Georges, M Gerbino, M Gervasi, RT Génova-Santos, T Ghigna, S Giardiello, C Gimeno-Amo, E Gjerløw, M Hazumi, S Henrot-Versillé, LT Hergt, E Hivon, K Kohri, E Komatsu, L Lamagna, M Lattanzi, C Leloup, M Lembo, M López-Caniego, G Luzzi, J Macias-Perez, B Maffei, S Masi, M Massa, S Matarrese, T Matsumura, S Micheli, A Moggi, M Monelli, L Montier, G Morgante, B Mot, L Mousset, R Nagata, P Natoli, A Novelli, I Obata, A Occhiuzzi, L Pagano, A Paiella, D Paoletti, G Pascual-Cisneros, V Pavlidou, F Piacentini, M Pinchera, G Pisano
– Journal of Cosmology and Astroparticle Physics
(2024)
2024,
009
(doi: 10.1088/1475-7516/2024/06/009)
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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