Christof Wetterich
Heidelberg University
Particle physicsEffective actionPhysicsSpontaneous symmetry breakingPhase transitionRenormalizationDark energyFunctional renormalization groupCosmologyQuantum electrodynamicsTheoretical physicsQuintessenceMathematical physicsAstrophysicsFermionScalar (mathematics)Quantum mechanicsRenormalization groupClassical mechanicsQuark
Publications 352
Many quintessence models possess scaling or attractor solutions where the fraction of dark energy follows the dominant component in previous epochs of the expansion, or phase transitions may happen close to matter-radiation equality time. A non-negligible early dark energy (EDE) fraction around matter-radiation equality could contribute to alleviate the H_0tension. We constrain the EDE fraction using two approaches: first, we use a fluid parameterization that mimics the plateaux of the domina...
We propose the great emptiness as a possible beginning of the Universe in the infinite past of physical time. In the beginning particles are very rare and effectively massless. Only expectation values of fields and average fluctuations characterize the lightlike vacuum of this empty Universe. Our observed inhomogeneous Universe can be extrapolated backwards to the lightlike vacuum in the infinite past, and therefore can have lasted eternally. There is no physical big bang singularity. Standard i...
#1Christof Wetterich (Heidelberg University)H-Index: 80
A simple probabilistic cellular automaton is shown to be equivalent to a relativistic fermionic quantum field theory with interactions. Occupation numbers for fermions are classical bits or Ising spins. The automaton acts deterministically on bit configurations. The genuinely probabilistic character of quantum physics is realized by probabilistic initial conditions. In turn, the probabilistic automaton is equivalent to the classical statistical system of a generalized Ising model. For a descript...
We investigate the dimensional crossover from three to two dimensions in an ultracold Fermi gas across the whole BCS-BEC crossover. Of particular interest is the strongly interacting regime as strong correlations are more pronounced in reduced dimensions. Our results are obtained from first principles within the framework of the functional renormalisation group (FRG). Here, the confinement of the transverse direction is imposed by means of periodic boundary conditions. We calculate the equation ...
#1Christof Wetterich (Heidelberg University)H-Index: 80
Quantum field theories with fundamental scale invariance admit a scale-free formulation of the functional integral and effective action in terms of scale invariant fields. They correspond to exact scaling solutions of functional flow equations. Such theories are highly predictive since all relevant parameters for deviations from the exact scaling solution vanish. The non-linear restrictions for scaling solutions can explain properties that would seem to need fine tuning of parameters from a pert...
#1Christof Wetterich (Heidelberg University)H-Index: 80
A particular version of the Thirring model with imaginary coupling can be represented as a cellular automaton. This interacting fermionic quantum field theory obeys a unitary time evolution and shows all properties of quantum mechanics. Cellular automata with probabilistic initial conditions can take the form of quantum theories. Our model exhibits interesting features as spontaneous symmetry breaking or solitons. The same model can be formulated as a generalized Ising model. This euclidean latt...
Einstein's general relativity can emerge from pregeometry, with the metric composed of more fundamental fields. We formulate euclidean pregeometry as a SO(4)- Yang-Mills theory. In addition to the gauge fields we include a vector field in the vector representation. The gauge - and diffeomorphism - invariant kinetic terms for these fields permit a well-defined euclidean functional integral, in contrast to metric gravity with the Einstein-Hilbert action. The propagators of all fields are well b...
#1Alessia Platania (Heidelberg University)H-Index: 16
#2Christof WetterichH-Index: 80
Abstract We discuss aspects of non-perturbative unitarity in quantum field theory. The additional ghost degrees of freedom arising in “truncations” of an effective action at a finite order in derivatives could be fictitious degrees of freedom. Their contributions to the fully-dressed propagator – the residues of the corresponding ghost-like poles – vanish once all operators compatible with the symmetry of the theory are included in the effective action. These “fake ghosts” do not indicate a viol...
#1Guillem Domènech (Heidelberg University)H-Index: 14
#2Mark D. GoodsellH-Index: 34
Last. Christof WetterichH-Index: 80
view all 3 authors...
A general prediction from asymptotically safe quantum gravity is the approximate vanishing of all quartic scalar couplings at the UV fixed point beyond the Planck scale. A vanishing Higgs doublet quartic coupling near the Planck scale translates into a prediction for the ratio between the mass of the Higgs boson M_Hand the top quark M_t If only the standard model particles contribute to the running of couplings below the Planck mass, the observed M_H\sim125\,{\rm GeV}results in the pred...
#1Astrid Eichhorn (University of Southern Denmark)H-Index: 35
#2Aaron Held (Imperial College London)H-Index: 10
Last. Christof Wetterich (Heidelberg University)H-Index: 80
view all 3 authors...
If a grand-unified extension of the asymptotically safe Reuter fixed-point for quantum gravity exists, it determines free parameters of the grand-unified scalar potential. All quartic couplings take their fixed-point values in the trans-Planckian regime. They are irrelevant parameters that are, in principle, computable for a given particle content of the grand unified model. In turn, the direction of spontaneous breaking of the grand-unified gauge symmetry becomes predictable. For the flow of th...
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