Dr Konstantinos Dimopoulos

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Research Interests

Particle Cosmology

My research area is Particle Cosmology. Cosmology is the study of the Universe as a system. Modern Cosmology is based on the Hot Big Bang (HBB) model, which provides a successful description of the Universe history as far back as the first second of its existence. However, the HBB leaves many questions unanswered. The answers hide in the elusive primordial era, when the Universe was so dense and hot that its evolution was determined by High Energy Physics phenomena. In fact, since the energy scale of the cosmology in the Early Universe is much higher than the scale of electroweak unification, one needs to employ Physics beyond the Standard Model to investigate the remaining mysteries. Particle Cosmology uses what is known or conjectured about the fundamental interactions in the context of Particle Theory for the study of the Early Universe.

Cosmic Inflation

One of my main areas of research is Cosmic Inflation. This can be defined as a period of accelerated expansion of space in the Early Universe. Inflation is a compelling solution to the problems of the HBB that have to do with why the Universe appears to be so big and so uniform on very large scales. It also provides an elegant way to generate the small perturbations in the density of the Universe, which are necessary for the formation of structures such as galaxies and galactic clusters. The existence and the characteristics of these Primordial Density Perturbations (PDP) have been observationally determined because they reflect themselves on the Cosmic Microwave Background Radiation (CMBR) by generating anisotropies and polarisation.

My research regarding Inflation aims to construct and study the dynamics of realistic inflationary models based on Particle Theory. I am also interested in the generation of the PDP during Inflation, which can be explored by investigating the behaviour and evolution of suitable fields, belonging to simple extensions of the Standard Model. These fields may or may not be related to inflationary expansion itself (if not they are called Curvatons). At this level there is also considerable interface between cosmology and String Theory, Branes and Large Extra Dimensions. It should be noted that recent, precise CMBR observations from the WMAP satellite, have confirmed the basic predictions of Inflation. Hence, Cosmic Inflation is now considered a necessary extension of HBB cosmology.

Quintessenctial Inflation

Another open issue for cosmologists today is the recent observation that the Universe seems to be engaging into an era of accelerated expansion at present. This is attributed to a mysterious Dark Energy substance, whose nature and origin is unknown. The simplest choice of Dark Energy is a Cosmological Constant. However, such a constant has to be incredibly fine-tunned (by hundreds of orders of magnitude) to explain the observations. Alternatively, it has been suggested that the Universe is undergoing a late period of inflation, driven by a scalar field called Quintessence; the fifth element after Dark Matter, neutrinos, photons and baryons. In my research I concentrate on the possibility that the field that drives Cosmic Inflation in the Early Universe is the same with Quintessence. The study of such Quintessential Inflation is not only economical but has the advantage of using a single theoretical framework to determine the global evolution of the Universe from extremely early times until the present. Primordial Magnetic Fields

Another area of my research is the possible generation of large-scale Primordial Magnetic Fields (PMFs) in the Early Universe. Such fields can be responsible for the observed intergalactic magnetic fields as well as the magnetic fields of the galaxies themselves. One can generate PMFs only in out-of thermal equilibrium conditions, because they break isotropy. Such opportunities exist during Phase Transitions in the Early Universe (at the breaking of symmetries of the fundamental interactions) and during Cosmic Inflation (when the Universe is supercooled because any preexisting entropy is inflated away).

Cosmic Vector Fields

Finally, in recent years I have pioneered the study of the effects of vector boson fields (such as the photon, i.e. the quantum of the electromagnetic field) on the PDP and CMBR. Such fields are produced in a similar manner as PMFs during Cosmic Inflation. I have shown that, under certain circumstances, vector boson fields can contribute significantly or even be solely responsible for the generation of the PDP. In contrast to scalar fields to which the PDP was attributed until now, vector boson fields have been observed in CERN (e.g. the W and Z massive gauge bosons). Moreover, they can give rise to distinct observational signatures on the CMBR, namely statistical anisotropy. This amounts to direction dependent patterns, which select a preferred direction on the microwave sky. Indeed, in recent years there is tantalising observational evidence that such a preferred direction may exist (manifested as alignment of the low multipoles of CMBR). Beyond the CMBR, statistical anisotropy may also reflect itself in the distribution of cosmic structures (e.g. rows of galaxies). Statistical anisotropy may well be observed in the near future by the Planck satellite, which was launched by ESA in May 2009. If so then one would have to involve vector boson fields in model-building inflation and in the generation of the PDP. This is the aim of my research. Theories beyond the Standard Model include many suitable candidates for cosmic vector fields such as the supermassive gauge bosons in Grand Unified Theories or fluxes in the extra dimensions needed for their stabilisation in String Theory.

Ultra slow-roll inflation demystified
Dimopoulos, K. 10/12/2017 In: Physics Letters B. 775, p. 262-265. 4 p.
Journal article

Initial conditions for inflation
Dimopoulos, K., Artymowski, M. 09/2017 In: Astroparticle Physics. 94, p. 11-16. 6 p.
Journal article

Quintessential inflation with α-attractors
Dimopoulos, K., Owen, C. 13/06/2017 In: Journal of Cosmology and Astroparticle Physics. 2017, 6, 27 p.
Journal article

Thermal Inflation with a thermal waterfall scalar field coupled to a light spectator scalar field
Dimopoulos, K., Lyth, D.H., Rumsey, A. 11/05/2017 In: Physical Review D. 95, 10, 14 p.
Journal article

Active galaxies can make axionic dark energy
Dimopoulos, K., Cormack, S. 12/2016 In: Astroparticle Physics. 85, p. 35-38. 4 p.
Journal article

How thermal inflation can save minimal hybrid inflation in supergravity
Dimopoulos, K., Owen, C. 12/10/2016 In: Journal of Cosmology and Astroparticle Physics. 16, 10, 9 p.
Journal article

Modelling inflation with a power-law approach to the inflationary plateau
Dimopoulos, K., Owen, C. 15/09/2016 In: Physical Review D. 94, 6, 10 p.
Journal article

Reheating in Gauss-Bonnet-coupled inflation
van de Bruck, C., Longden, C., Dimopoulos, K. 6/07/2016 In: Physical Review D. 94, 2, 12 p.
Journal article

Shaft inflation and the Planck satellite observations
Dimopoulos, K. 2015 In: Proceedings of Science. Proceedings of Science 8 p.
Conference contribution

Shaft inflation
Dimopoulos, K. 30/07/2014 In: Physics Letters B. 735, p. 75-78. 4 p.
Journal article

Reconciliation of high energy scale models of inflation with Planck
Ashoorioon, A., Dimopoulos, K., M. Sheikh-Jabbari, M., Shiu, G. 14/02/2014 In: Journal of Cosmology and Astroparticle Physics. 2014, 2, 12 p.
Journal article

Inflationary buildup of a vector field condensate and its cosmological consequences
Bueno Sanchez, J., Dimopoulos, K. 10/01/2014 In: Journal of Cosmology and Astroparticle Physics. 2014, 1, 32 p.
Journal article

Non-bunch-Davis initial state reconciles chaotic models with BICEP and Planck
Ashoorioon, A., Dimopoulos, K., M. Sheikh-Jabbari, M., Shiu, G. 2014 In: Physics Letters B. 737, p. 98-102. 5 p.
Journal article

D-branes and cosmic structure
Wills, D., Dimopoulos, K., Zavala, I. 07/2013 In: Proceedings of the Barcelona Postgrad Encounters in Fundamental Physics. Spain : Daniel Fernandez Moreno p. 179-190. 12 p.
Paper

Statistical Anisotropy from Vector Curvaton in D-brane Inflation
Dimopoulos, K., Wills, D., Zavala, I. 1/03/2013 In: Nuclear Physics B. 868, 1, p. 120-155. 36 p.
Journal article

Correlated curvature perturbations and magnetogenesis from the GUT gauge bosons
Dimopoulos, K. 02/2013 In: Astroparticle Physics. 42, p. 86-89. 4 p.
Journal article

The hybrid curvaton
Dimopoulos, K., Kohri, K., Matsuda, T. 26/06/2012 In: Physical Review D. 85, 12, 7 p.
Journal article

Parity Violating Statistical Anisotropy
Dimopoulos, K., Karciauskas, M. 6/06/2012 In: Journal of High Energy Physics. 2012, 6, 35 p.
Journal article

The inflating curvaton
Dimopoulos, K., Kohri, K., Lyth, D., Matsuda, T. 12/03/2012 In: Journal of Cosmology and Astroparticle Physics. 03, p. 0-8. 9 p.
Journal article

Statistical Anisotropy and the Vector Curvaton Paradigm
Dimopoulos, K. 5/03/2012 In: International Journal of Modern Physics D. 21, 3, p. 1-26. 26 p.
Journal article

Eliminating the eta-problem in SUGRA hybrid inflation with vector backreaction
Dimopoulos, K., Lazarides, G., Wagstaff, J. 15/02/2012 In: Journal of Cosmology and Astroparticle Physics. 02, p. 0-26. 27 p.
Journal article

The gravitino problem in supersymmetric warm inflation
Bueno Sanchez, J.C., Bastero Gil, M., Berera, A., Dimopoulos, K., Kohri, K. 9/03/2011 In: Journal of Cosmology and Astroparticle Physics. 2011, 3
Journal article

Particle Production of Vector Fields: Scale Invariance is Attractive
Wagstaff, J., Dimopoulos, K. 25/01/2011 In: Physical Review D. 83, 2, 33 p.
Journal article

The quantum origin of cosmic structure: theory and observations
Dimopoulos, K. 2011 In: Journal of Physics: Conference Series. 283, 1, 22 p.
Journal article

Vector curvaton with varying kinetic function
Dimopoulos, K., Karciauskas, M., Wagstaff, J.M. 29/01/2010 In: Physical Review D. 81, 2, p. 023522.
Journal article

Vector curvaton without instabilities.
Dimopoulos, K., Karciauskas, M., Wagstaff, J.M. 25/01/2010 In: Physics Letters B. 683, 4-5, p. 298-301. 4 p.
Journal article

Where galaxies really come from.
Dimopoulos, K. 1/11/2009 In: Contemporary Physics. 50, 6, p. 633-646. 14 p.
Journal article

Anisotropic non-Gaussianity from vector field perturbations
Karciauskas, M., Dimopoulos, K., Lyth, D.H. 15/07/2009 In: Physical Review D. 80, 2, p. 023509.
Journal article

Statistical anisotropy of the curvature perturbation from vector field perturbations.
Dimopoulos, K., Karciauskas, M., Lyth, D.H., Rodriguez, Y. 26/05/2009 In: Journal of Cosmology and Astroparticle Physics. 2009, 5, p. 013.
Journal article

Non-minimally coupled vector curvaton.
Dimopoulos, K., Karciauskas, M. 29/07/2008 In: Journal of High Energy Physics. 2008, 07, 10 p.
Journal article

Warm hilltop inflation
Bueno-Sanchez, J.C., Bastero Gil, M., Berera, A., Dimopoulos, K. 15/06/2008 In: Physical Review D. 77, 12
Journal article

Density Perturbations in the Universe from Massive Vector Fields.
Dimopoulos, K. 20/11/2007 In: AIP Conference Proceedings. 957, 1, p. 387-390. 4 p.
Journal article

Curvaton reheating allows a TeV Hubble scale in non-oscillatory inflation.
Bueno-Sanchez, J.C., Dimopoulos, K. 9/11/2007 In: Journal of Cosmology and Astroparticle Physics. 2007, 11, p. 007.
Journal article

Trapped quintessential inflation in the context of flux compactifications.
Bueno-Sanchez, J.C., Dimopoulos, K. 4/10/2007 In: Journal of Cosmology and Astroparticle Physics. 2007, 10, p. 002.
Journal article

Supergravity inspired Vector curvaton
Dimopoulos, K. 14/09/2007 In: Physical Review D. 76, 6197
Journal article

A-term inflation and the minimal supersymmetric standard model.
Bueno-Sanchez, J.C., Dimopoulos, K., Lyth, D.H. 16/01/2007 In: Journal of Cosmology and Astroparticle Physics. 2007, 1, p. 015.
Journal article

Trapped Quintessential Inflation from Flux Compactifications.
Dimopoulos, K. 2007 In: IDM 2006: 6th International Workshop On The Identification Of Dark Matter. World Scientific p. 635-646. 12 p.
Chapter

Trapped Quintessential Inflation.
Bueno-Sanchez, J.C., Dimopoulos, K. 16/11/2006 In: Physics Letters B. 642, 4, p. 294-301. 8 p.
Journal article

Can a vector field be responsible for the curvature perturbation in the Universe?
Dimopoulos, K. 2/10/2006 In: Physical Review D. 74, 8
Journal article

Inflation at the TeV scale with a PNGB curvaton.
Dimopoulos, K. 16/03/2006 In: Physics Letters B. 634, 4, p. 331-339. 9 p.
Journal article

Modular inflation and the orthogonal axion as curvaton.
Dimopoulos, K., Lazarides, G. 15/01/2006 In: Physical Review D. 73, 2
Journal article

The Density Perturbation in the Universe: Beyond the Inflaton Paradigm.
Axenides, M., Dimopoulos, K., Kehagias, A. 11/2005 In: Nuclear Physics B - Proceedings Supplements. 148
Journal article

Cosmic superstrings and primordial magnetogenesis.
Davis, A., Dimopoulos, K. 15/08/2005 In: Physical Review D. 72, 4, p. 043517.
Journal article

Hybrid inflation without flat directions and without primordial black holes.
Dimopoulos, K., Axenides, M. 17/06/2005 In: Journal of Cosmology and Astroparticle Physics. 2005, 06, p. 008.
Journal article

Low scale inflation and the curvaton mechanism.
Dimopoulos, K., Lyth, D.H., Rodriguez Garcia, Y. 11/03/2005 In: Journal of High Energy Physics. 2005, 02, p. 055.
Journal article

Curvaton and QCD axion in supersymmetric theories
Chun, E.J., Dimopoulos, K., Lyth, D.H. 15/11/2004 In: Physical Review D. 70, 10
Journal article

Hybrid dark sector: Locked quintessence and dark matter.
Axenides, M., Dimopoulos, K. 19/07/2004 In: Journal of Cosmology and Astroparticle Physics. 2004, 07, p. 010.
Journal article

Models of inflation liberated by the curvaton hypothesis
Dimopoulos, K., Lyth, D.H. 15/06/2004 In: Physical Review D. 69, 12
Journal article

Modular hybrid inflation without flat directions and the curvaton.
Dimopoulos, K. 2004 In: 39th Rencontres De Moriond Workshop On Exploring The Universe: Contents And Structures Of The Universe.
Chapter

Curvaton dynamics
Dimopoulos, K., Lazarides, G., Lyth, D.H., Ruiz de Austri, R. 15/12/2003 In: Physical Review D. 68, 12
Journal article

Curvaton hypothesis and the eta-problem of quintessential inflation, with and without branes.
Dimopoulos, K. 15/12/2003 In: Physical Review D. 68, 12
Journal article

The Curvaton as a pseudoNambu-Goldstone boson.
Dimopoulos, K., Lyth, D.H., Notari, A., Riotto, A. 28/10/2003 In: Journal of High Energy Physics. 2003, 07, p. 053.
Journal article

The Peccei-Quinn field as curvaton.
Dimopoulos, K., Lazarides, G., Lyth, D.H., Ruiz de Austri, R. 25/05/2003 In: Journal of High Energy Physics. 2003, 05, p. 057.
Journal article

Modeling quintessential inflation.
Dimopoulos, K., Valle, J.W.F. 12/2002 In: Astroparticle Physics. 18, 3, p. 287-306. 20 p.
Journal article

Natural magnetogenesis from inflation
Dimopoulos, K., Prokopec, T., Tornkvist, O., Davis, A. 22/02/2002 In: Physical Review D. 65, 6
Journal article

Galactic magnetic fields as a consequence of inflation.
Dimopoulos, K. 2002 In: 2nd Hellenic Cosmology Conference.
Chapter

Modeling quintessential inflation with branes.
Dimopoulos, K. 2002 In: 18th IAP Colloquium On The Nature Of Dark Energy: Observational And Theoretical Results On The Accelerating Universe. p. 275-278. 4 p.
Chapter

Towards a model of quintessential inflation.
Dimopoulos, K. 04/2001 In: Nuclear Physics B - Proceedings Supplements. 95, 1-3, p. 70-73. 4 p.
Journal article

Primordial spectrum of gauge fields from inflation.
Davis, A., Dimopoulos, K., Prokopec, T., Tornkvist, O. 8/03/2001 In: Physics Letters B. 501, 3-4, p. 165-172. 8 p.
Journal article

Models of quintessential inflation.
Dimopoulos, K. 2001 In: International Workshop On Particle Physics And The Early Universe (COSMO-01).
Chapter

Large scale primordial magnetic fields from inflation and preheating
Tornkvist, O., Davis, A., Dimopoulos, K., Prokopec, T. 2000 In: COSMOLOGY AND PARTICLE PHYSICS: CAPP 2000: Proceedings. Melville, N.Y. : American Institute of Physics p. 443-446. 4 p.
Chapter

Cosmological consequences of superconducting string networks.
Dimopoulos, K., Davis, A. 28/01/1999 In: Physics Letters B. 446, 3-4, p. 238-246. 9 p.
Journal article

Primordial magnetic fields from superconducting cosmic strings.
Dimopoulos, K. 15/04/1998 In: Physical Review D. 57, 8, p. 4629-4641. 13 p.
Journal article

Friction domination with superconducting strings
Dimopoulos, K., Davis, A. 15/01/1998 In: Physical Review D. 57, 2, p. 692-701. 10 p.
Journal article

Generating primordial magnetic fields from superconducting cosmic strings.
Dimopoulos, K. 1998 In: COSMO 97: 1st International Workshop on Particle Physics and the Early Universe. World Scientific p. 411-413. 3 p.
Chapter

Primordial magnetic fields in false vacuum inflation
Davis, A., Dimopoulos, K. 15/06/1997 In: Physical Review D. 55, 12, p. 7398-7414. 17 p.
Journal article

Evolution of primordial magnetic fields.
Dimopoulos, K., Davis, A. 2/01/1997 In: Physics Letters B. 390, 1-4, p. 87-96. 10 p.
Journal article