Very large scale structures in growing neutrino quintessence (2009)
Wintergerst, Nico, Pettorino, Valeria, Mota, David F., Wetterich, Christof
A quintessence scalar field or cosmon interacting with neutrinos can have important effects on cosmological structure formation. Within growing neutrino models the coupling becomes effective only in...
Peculiar Velocity Anomaly from Forces Beyond Gravity? (2009)
Ayaita, Youness, Weber, Maik, Wetterich, Christof
We address recently reported anomalously large bulk flows on scales of 100 Mpc/h and beyond. These coherent motions of galaxies challenge the standard LCDM concordance model as well as a large class...
Too few spots in the Cosmic Microwave Background (2009)
Ayaita, Youness, Weber, Maik, Wetterich, Christof
We investigate the abundance of large-scale hot and cold spots in the WMAP-5 temperature maps and find considerable discrepancies compared to Gaussian simulations based on the LCDM best-fit model....
Growing neutrino cosmology (2009)
Wetterich, Christof, Pettorino, Valeria
In growing neutrino models, the neutrino mass increases in time and stops the dynamical evolution of a dark energy scalar field, thus explaining the 'why now' problem. A new attractive force,...
Clustering in growing neutrino cosmologies (2009)
Pettorino, Valeria, Mota, David F., Robbers, Georg, Wetterich, Christof
We show that growing neutrino models, in which the growing neutrino mass stops the dynamical evolution of a dark energy scalar field, lead to a substantial neutrino clustering on the scales of...
Competing bounds on the present-day time variation of fundamental constants (2008)
Dent, Thomas, Stern, Steffen, Wetterich, Christof
We compare the sensitivity of a recent bound on time variation of the fine structure constant from optical clocks with bounds on time varying fundamental constants from atomic clocks sensitive to the...
Asymptotically free four-fermion interactions and electroweak symmetry breaking (2008)
Schwindt, Jan-Markus, Wetterich, Christof
We investigate the fermions of the standard model without a Higgs scalar. Instead, we consider a non-local four-quark interaction in the tensor channel which is characterized by a single...
Time variation of fundamental couplings and dynamical dark energy (2008)
Dent, Thomas, Stern, Steffen, Wetterich, Christof
Scalar field dynamics may give rise to a nonzero cosmological variation of fundamental constants. Within different scenarios based on the unification of gauge couplings, the various claimed...
Unifying cosmological and recent time variations of fundamental couplings (2008)
Dent, Thomas, Stern, Steffen, Wetterich, Christof
A number of positive and null results on the time variation of fundamental constants have been reported. It is difficult to judge whether or not these claims are mutually consistent, since the...
Cosmon Lumps and Horizonless Black Holes (2008)
Krueger, Timm, Neubert, Matthias, Wetterich, Christof
We investigate non-linear, spherically symmetric solutions to the coupled system of a quintessence field and Einstein gravity. In the presence of a scalar potential, we find regular solutions that to...
Chiral tensor fields and spontaneous breaking of Lorentz symmetry (2007)
Schwindt, Jan-Markus, Wetterich, Christof
Antisymmetric tensor fields interacting with quarks and leptons have been proposed as a possible solution to the gauge hierarchy problem. We compute the one-loop beta function for a quartic...
Effective Nonlocal Euclidean Gravity (2007)
A nonlocal form of the effective gravitational action could cure the unboundedness of euclidean gravity with Einstein action. On sub-horizon length scales the modified gravitational field equations...
Light fermion masses and chiral freedom (2007)
Within the scenario of chiral freedom we compute the quark and lepton masses of the first two generations in terms of their chiral couplings. This allows us to make a rough estimate of the size of...
Amendola, Luca, Baldi, Marco, Wetterich, Christof
We investigate quintessence cosmologies with a matter component consisting of particles with an increasing mass. While negligible in early cosmology, the appearance of a growing matter component has...
Primordial nucleosynthesis as a probe of fundamental physics parameters (2007)
Dent, Thomas, Stern, Steffen, Wetterich, Christof
We analyze the effect of variation of fundamental couplings and mass scales on primordial nucleosynthesis in a systematic way. The first step establishes the response of primordial element abundances...
Doran, Michael, Robbers, Georg, Wetterich, Christof
The first three years of observation of the Wilkinson Microwave Anisotropy Probe (WMAP) have provided the most precise data on the anisotropies of the cosmic microwave background (CMB) to date. We...
Do Instantons Like a Colorful Background? (2006)
Gies, Holger, Jaeckel, Joerg, Pawlowski, Jan M., Wetterich, Christof
We investigate chiral symmetry breaking and color symmetry breaking in QCD. The effective potential of the corresponding scalar condensates is discussed in the presence of non-perturbative...
The cosmological constant problem in codimension-two brane models (2005)
Schwindt, Jan-Markus, Wetterich, Christof
We discuss the possibility of a dynamical solution to the cosmological constant problem in the contaxt of six-dimensional Einstein-Maxwell theory. A definite answer requires an understanding of the...
Observational constraints on the dark energy density evolution (2005)
Doran, Michael, Karwan, Khamphee, Wetterich, Christof
We constrain the evolution of the dark energy density from Cosmic Microwave Background, Large Scale Structure and Supernovae Ia measurements. While Supernovae Ia are most sensitive to the equation of...
Non-linear Structure Formation in Cosmologies with Early Dark Energy (2005)
Bartelmann, Matthias, Doran, Michael, Wetterich, Christof
We argue that a few per cent of "Early Dark Energy" can be detected by the statistics of nonlinear structures. The presence of Dark Energy during linear structure formation is natural in models where...
Dark energy cosmologies for codimension-two branes (2005)
Schwindt, Jan-Markus, Wetterich, Christof
A six-dimensional universe with two branes in the "football-shaped" geometry leads to an almost realistic cosmology. We describe a family of exact solutions with time dependent characteristic size of...
Nucleosynthesis and the variation of fundamental couplings (2004)
Mueller, Christian M., Schaefer, Gregor, Wetterich, Christof
We determine the influence of a variation of the fundamental ``constants'' on the predicted helium abundance in Big Bang Nucleosynthesis. The analytic estimate is performed in two parts: the first...
Towards a renormalizable standard model without fundamental Higgs scalar (2003)
Gies, Holger, Jaeckel, Joerg, Wetterich, Christof
We investigate the possibility of constructing a renormalizable standard model with purely fermionic matter content. The Higgs scalar is replaced by point-like fermionic self-interactions with...
First Order Chiral Phase Transition from a Six-fermion ''Instanton''-Interaction (2003)
Jaeckel, Joerg, Wetterich, Christof
We compute the first order chiral phase transition for an instanton motivated quark model with a local six-quark interaction. In order to compare different solutions of the gap equation we compute...
Schwindt, Jan-Markus, Wetterich, Christof
We discuss the properties of codimension-two branes and compare them to codimension-one branes. In particular, we show that for deficit angle branes the brane energy momentum tensor is uniquely...
Gauge-Invariant Initial Conditions and Early Time Perturbations in Quintessence Universes (2003)
Doran, Michael, Mueller, Christian M., Schaefer, Gregor, Wetterich, Christof
We present a systematic treatment of the initial conditions and evolution of cosmological perturbations in a universe containing photons, baryons, neutrinos, cold dark matter, and a scalar...
Early Quintessence in Light of WMAP (2003)
Caldwell, Robert R., Doran, Michael, Mueller, Christian M., Schaefer, Gregor, Wetterich, Christof
We examine the cosmic microwave background (CMB) anisotropy for signatures of early quintessence dark energy -- a non-negligible quintessence energy density during the recombination and structure...
Universality of spontaneous chiral symmetry breaking in gauge theories (2002)
Gies, Holger, Wetterich, Christof
We investigate one-flavor QCD with an additional chiral scalar field. For a large domain in the space of coupling constants, this model belongs to the same universality class as QCD, and the effects...
Bosonic effective action for interacting fermions (2002)
We compare different versions of a bosonic description for systems of interacting fermions, with particular emphasis on the free energy functional. The bosonic effective action makes the issue of...
Flow Equations without Mean Field Ambiguity (2002)
Jaeckel, Joerg, Wetterich, Christof
We compare different methods used for non-perturbative calculations in strongly interacting fermionic systems. Mean field theory often shows a basic ambiguity related to the possibility to perform...
Renormalization flow from UV to IR degrees of freedom (2002)
Gies, Holger, Wetterich, Christof
Within the framework of exact renormalization group flow equations, a scale-dependent transformation of the field variables provides for a continuous translation of UV to IR degrees of freedom. Using...
Quintessence and the cosmological constant (2002)
Doran, Michael, Wetterich, Christof
Quintessence -- the energy density of a slowly evolving scalar field -- may constitute a dynamical form of the homogeneous dark energy in the universe. We review the basic idea in the light of the...
Structure Formation and the Time Dependence of Quintessence (2001)
Doran, Michael, Schwindt, Jan-Markus, Wetterich, Christof
We discuss the influence of dark energy on structure formation, especially the effects on \sigma_8. Our interest is particularly focused on quintessence models with time-dependent equation of state...
Renormalization Flow of Bound States (2001)
Gies, Holger, Wetterich, Christof
A renormalization group flow equation with a scale-dependent transformation of field variables gives a unified description of fundamental and composite degrees of freedom. In the context of the...
Correlation functions for composite operators in the Hubbard model (2001)
Baier, Tobias, Bick, Eike, Wetterich, Christof
We compute the correlation functions for antiferromagnetic and d-wave superconducting fermion bilinears in a generalized mean field type approximation for the Hubbard model. For high temperature our...
Constraining Quintessence with the New CMB Data (2001)
Doran, Michael, Lilley, Matthew, Wetterich, Christof
The CMB data recently released by BOOMERANG and MAXIMA suggest that the anisotropy spectrum has a third peak in the range 800
The Influence of Quintessence on the Separation of CMB Peaks (2001)
Doran, Michael, Lilley, Matthew, Schwindt, Jan, Wetterich, Christof
A hypothetical dark energy component may have an equation of state that is different from a cosmological constant and possibly even changing in time. The spacing of the cosmic microwave background...
Connection between Chiral Symmetry Restoration and Deconfinement (2001)
We propose a simple explanation for the connection between chiral symmetry restoration and deconfinement in QCD at high temperature. In the Higgs description of the QCD vacuum both spontaneous chiral...
Evolution equations for the effective four-quark interactions in QCD (2000)
Meggiolaro, Enrico, Wetterich, Christof
A nonperturbative renormalization group equation describes how the momentum dependent four-quark vertex depends on an infrared cutoff. We find a quasilocal one-particle irreducible piece generated by...
Quintessence and the Separation of CMB Peaks (2000)
Doran, Michael, Lilley, Matthew, Schwindt, Jan, Wetterich, Christof
We propose that it should be possible to use the CMB to discriminate between dark energy models with different equations of state, including distinguishing a cosmological constant from many models of...
Phase Transitions in liquid Helium 3 (2000)
Kindermann, Markus, Wetterich, Christof
The phase transitions of liquid Helium 3 are described by truncations of an exact nonperturbative renormalization group equation. The location of the first order transition lines and the jump in the...
Exact and Truncated Dynamics in Nonequilibrium Field Theory (2000)
Aarts, Gert, Bonini, Gian Franco, Wetterich, Christof
Nonperturbative dynamics of quantum fields out of equilibrium is often described by the time evolution of a hierarchy of correlation functions, using approximation methods such as Hartree, large N,...
Spontaneous symmetry breaking in the colored Hubbard model (2000)
Baier, Tobias, Bick, Eike, Wetterich, Christof
The Hubbard model is reformulated in terms of different ``colored'' fermion species for the electrons or holes at different lattice sites. Antiferromagnetic ordering or d-wave superconductivity can...
On Thermalization in Classical Scalar Field Theory (2000)
Aarts, Gert, Bonini, Gian Franco, Wetterich, Christof
Thermalization of classical fields is investigated in a \phi^4 scalar field theory in 1+1 dimensions, discretized on a lattice. We numerically integrate the classical equations of motion using...
Time evolution of correlation functions and thermalization (1999)
Bonini, Gian Franco, Wetterich, Christof
We investigate the time evolution of a classical ensemble of isolated periodic chains of O(N)-symmetric anharmonic oscillators. Our method is based on an exact evolution equation for the time...
The QCD-vacuum is characterized by the Higgs phenomenon for colored scalar fields. In this dual picture the gluons appear as the octet of vector mesons. Also quarks and baryons are identified....
Time evolution of correlation functions in Non-equilibrium Field Theories (1997)
Bettencourt, Luis M. A., Wetterich, Christof
We investigate the non-equilibrium properties of an N-component scalar field theory. The time evolution of the correlation functions for an arbitrary ensemble of initial conditions is described by an...
Effective Quark Interactions and QCD-Propagators (1997)
Bergerhoff, Bastian, Wetterich, Christof
We compute the momentum dependence of the effective four quark interaction in QCD after integrating out the gluons. Our method is based on a truncation of exact renormalization group equations which...
Quantum Dynamics in Classical Time Evolution of Correlation Functions (1997)
The time-dependence of correlation functions under the influence of classical equations of motion is described by an exact evolution equation. For conservative systems thermodynamic equilibrium is a...
Time Evolution of Non-Equilibrium Effective Action (1996)
The time evolution of correlation functions in statistical systems is described by an exact functional differential equation for the corresponding generating functionals. This allows for a systematic...
Electroweak Phase Transition in the Early Universe ? (1996)
Bergerhoff, Bastian, Wetterich, Christof
Existence and properties of the electroweak phase transition in the early universe depend strongly on the mass of the Higgs scalar M_H. There is presumably no true symmetry restoration at high...
Integrating out Gluons in Flow Equations (1996)
We present an exact nonperturbative flow equation for the average action for quarks which incorporates the effects of gluon fluctuations. With suitable truncations this allows one to compute...
Systematic Resummed Perturbation Theory (1996)
A systematic loop expansion is formulated in terms of full propagators and vertices. It is based on an expansion of the general solution of an exact non-perturbative flow equation.
Nonperturbative Condensates in the Electroweak Phase-Transition (1995)
Bergerhoff, Bastian, Wetterich, Christof
We discuss the electroweak phase-transition in the early universe, using non-perturbative flow equations for a computation of the free energy. For a scalar mass above $\sim 70$ GeV, high-temperature...
High Temperature Field Theory Beyond Perturbation Theory (1994)
For realistic values of the Higgs boson mass the high temperature electroweak phase transition cannot be described perturbatively. The symmetric phase is governed by a strongly interacting $SU(2)$...