Mikjel Thorsrud

• Normann, Ben David; Ricciardone, Angelo; Hervik, Sigbjørn & Thorsrud, Mikjel (2022). A study of inhomogeneous massless scalar gauge fields in cosmology. International Journal of Modern Physics, Conference Series. ISSN 2010-1945. s. 1378–1883. doi: 10.1142/9789811258251_0199. Fulltekst i vitenarkiv
• Thorsrud, Mikjel; Normann, Ben David & Pereira, Thiago dos Santos (2020). Extended FLRW models: dynamical cancellation of cosmological anisotropies. Classical and Quantum Gravity. ISSN 0264-9381. 37(6), s. 1–37. doi: 10.1088/1361-6382/ab6f7f.
• Thorsrud, Mikjel (2019). Bianchi models with a free massless scalar field: invariant sets and higher symmetries. Classical and Quantum Gravity. ISSN 0264-9381. 36(23). doi: 10.1088/1361-6382/ab45b3.
• Thorsrud, Mikjel (2018). Balancing anisotropic curvature with gauge fields in a class of shear-free cosmological models. Classical and Quantum Gravity. ISSN 0264-9381. 35(9). doi: 10.1088/1361-6382/aab65a.
• Normann, Ben David; Hervik, Sigbjørn; Ricciardone, Angelo & Thorsrud, Mikjel (2018). Bianchi cosmologies with p-form gauge fields. Classical and Quantum Gravity. ISSN 0264-9381. 35(9). doi: 10.1088/1361-6382/aab3a7.
• Ramazanov, Sabir; Rubtsov, Grigory; Thorsrud, Mikjel & Urban, Federico (2017). General quadrupolar statistical anisotropy: Planck limits. Journal of Cosmology and Astroparticle Physics (JCAP). ISSN 1475-7516. 2017(3). doi: 10.1088/1475-7516/2017/03/039.
• Thorsrud, Mikjel (2015). Quintessence with Kaluza-Klein type couplings to matter and an isotropy-violating vector field, The Thirteenth Marcel Grossmann Meeting: On Recent Developments in Theoretical and Experimental General Relativity, Astrophysics, and Relativistic Field Theories. World Scientific. ISSN 978-981-4612-14-2. s. 1561–1563. doi: 10.1142/9789814623995_0224. Vis sammendrag

  We study the dynamics of a scalar field with Kaluza-Klein type couplings to cold dark matter and an isotropy-violating vector field. The vector coupling, f2(ϕ)F2, has been studied thoroughly in the context of inflation recently. We generalize the model to a dark energy context and study the cosmological consequences. We find a rich set of exact anisotropic power-law solutions and identify a strong vector coupling regime where the anisotropy is controllable and all solutions are close to the ΛCDM limit.

• Thorsrud, Mikjel; Mota, David & Urban, Federico (2014). Local observables in a landscape of infrared gauge modes. Physics Letters B. ISSN 0370-2693. 733, s. 140–143. doi: 10.1016/j.physletb.2014.04.028. Fulltekst i vitenarkiv
• Thorsrud, Mikjel; Urban, Federico & Mota, David (2014). Statistics of anisotropies in inflation with spectator vector fields. Journal of Cosmology and Astroparticle Physics (JCAP). ISSN 1475-7516. 2014(4). doi: 10.1088/1475-7516/2014/04/010.
• Jimenez, Jose Beltran; Durrer, Ruth; Heisenberg, L. & Thorsrud, Mikjel (2013). Stability of Horndeski vector-tensor interactions. Journal of Cosmology and Astroparticle Physics (JCAP). ISSN 1475-7516. 2013. doi: 10.1088/1475-7516/2013/10/064.
• Barrow, J. D.; Thorsrud, Mikjel & Yamamota, Kei (2013). Cosmologies in Horndeski's second-order vector-tensor theory. Journal of High Energy Physics (JHEP). ISSN 1126-6708. doi: 10.1007/JHEP02(2013)146.
• Thorsrud, Mikjel; Mota, David & Hervik, Sigbjørn (2012). Cosmology of a scalar field coupled to matter and an isotropy-violating Maxwell field. Journal of High Energy Physics (JHEP). ISSN 1126-6708. doi: 10.1007/JHEP10(2012)066.
• Hervik, Sigbjørn; Mota, David & Thorsrud, Mikjel (2011). Inflation with stable anisotropic hair: is it cosmologically viable? Journal of High Energy Physics (JHEP). ISSN 1126-6708. doi: 10.1007/JHEP11(2011)146.

Se alle arbeider i Cristin

• Thorsrud, Mikjel (2019). Gravitasjon på skrivebordet.
• Thorsrud, Mikjel (2018). Shear-Free Cosmological Solutions And Their Stability.
• Thorsrud, Mikjel (2015). Horndeski’s Vector-Tensor Theory. Vis sammendrag

  Horndeski formulated a most general vector-tensor theory that reduces to ordinary electrodynamics in a flat spacetime, in which the dynamical equations are of second order and the vector field respects the gauge symmetry. The theory is remarkably simple containing only a single free parameter which controls the strength of the vector's coupling to gravity. In this talk I will give a short introduction to the theory and report on our attempts to understand its stability and phenomenological consequences, focusing mainly on a cosmological context.

• Urban, Federico; Mota, David & Thorsrud, Mikjel (2014). Bubble observers in Bubbland [ARISF, Paris, pp. 255-258 (2014)]. Vis sammendrag

• Thorsrud, Mikjel (2013). Inflation with vector interactions. Vis sammendrag

  Vector fields are usually assumed to decay away exponentially fast during inflation and therefore ignored. Nevertheless, with an appropriate coupling to the inflaton, vectors may play an interesting role. In this talk I will first give an introduction to inflation with the f^2F^2 interaction and review some of its rich phenomenology. Next I will focus on the role of super horizon vector fluctuations and their contribution to the primordial power spectrum. Contrary to the contribution from the background vector, their contribution is not deterministically determined by background parameters. Instead the huge cosmic variance associated with large scale fluctuations requires a stochastic approach and the prediction is in terms of a probability distribution function (PDF) which we estimate by Monte-Carlo simulations.

• Thorsrud, Mikjel (2013). Infrared corrections to the primordial power spectrum in the f2(φ)F2 mechanism.
• Thorsrud, Mikjel (2013). Cosmologies in Horndeski's vector-tensor theory. Vis sammendrag

  In 1976 Horndeski formulated a most general vector-tensor theory in which the vector field respects the gauge symmetry and the resulting dynamical equations are of second order. In a flat spacetime background the theory reduces to ordinary electrodynamics. The theory is remarkably simple containing only a single free parameter which controlst he strength of the vector's coupling to gravity. Until very recently, the cosmological consequences of this theory remained unexplored. In this talk I will introduce you to the theory and tell you about our attempts to understand its consequences in a cosmological context.

• Thorsrud, Mikjel (2012). Doubly Coupled Quintessence. Vis sammendrag

  Motivated by the couplings of the dilaton in four-dimensional effective actions, we investigate the cosmological consequences of a scalar field coupled both to matter and a Maxwell-type vector field. The vector field has a background isotropy-violating component. New anisotropic scaling solutions which can be responsible for the matter and dark energy dominated epochs are identified and explored. For a large parameter region the universe expands almost isotropically. Using that the CMB quadrupole is extremely sensitive to shear, we constrain the ratio of the matter coupling to the vector coupling to be less than 10-5. Moreover, we identify a large parameter region, corresponding to a strong vector coupling regime, yielding exciting and viable cosmologies close to the LCDM limit.

• Thorsrud, Mikjel (2012). Dynamical System Approach to Non-minimal Matter Couplings.
• Thorsrud, Mikjel (2012). Quintessence with Kaluza-Klein type couplings to matter and an isotropy-violating vector field. Vis sammendrag

  We study the dynamics of a scalar field with Kaluza-Klein type couplings to cold dark matter and an isotropy-violating vector field. The vector coupling, f2(ϕ)F2, has been studied thoroughly in the context of inflation recently. We generalize the model to a dark energy context and study the cosmological consequences. We find a rich set of exact anisotropic power-law solutions and identify a strong vector coupling regime where the anisotropy is controllable and all solutions are close to the ΛCDM limit.

• Thorsrud, Mikjel (2011). Inflation with Stable Anisotropic Hair.
• Thorsrud, Mikjel (2011). Stability of Anisotropic Inflation.
• Thorsrud, Mikjel (2014). Cosmologies with Gauge Vector Interactions. Akademika forlag. ISSN 1501-7710.
• Thorsrud, Mikjel (2010). Post-Newtonian methods and the gravito-electromagnetic analogy. 7Letras.

Se alle arbeider i Cristin