• Anomalous electrodynamics of neutral pion matter in strong magnetic fields 

      Brauner, Tomas; Kadam, Saurabh (Journal article; Peer reviewed, 2017-03)
      The ground state of quantum chromodynamics in sufficiently strong external magnetic fields and at moderate baryon chemical potential is a chiral soliton lattice (CSL) of neutral pions [1]. We investigate the interplay ...
    • Anomalous low-temperature thermodynamics of QCD in strong magnetic fields 

      Brauner, Tomas; Kadam, Saurabh (Journal article; Peer reviewed, 2017-11)
      The thermodynamics of quantum chromodynamics at low temperatures and in sufficiently strong magnetic fields is governed by neutral pions. We analyze the interacting system of neutral pions and photons at zero baryon chemical ...
    • Anomaly-Induced Inhomogeneous Phase in Quark Matter without the Sign Problem 

      Brauner, Tomas; Filios, Georgios; Kolesova, Helena (Peer reviewed; Journal article, 2019)
      We demonstrate the existence of an anomaly-induced inhomogeneous phase in a class of vectorlike gauge theories without the sign problem, thus disproving the long-standing conjecture that the absence of the sign problem ...
    • Chiral soliton lattice and charged pion condensation in strong magnetic fields 

      Brauner, Tomas; Yamamoto, Naoki (Journal article; Peer reviewed, 2017-04)
      The Chiral Soliton Lattice (CSL) is a state with a periodic array of topological solitons that spontaneously breaks parity and translational symmetries. Such a state is known to appear in chiral magnets. We show that CSL ...
    • Chiral soliton lattice in QCD-like theories 

      Brauner, Tomas; Filios, Georgios; Kolesova, Helena (Peer reviewed; Journal article, 2019)
      Recently, it has been shown that the ground state of quantum chromodynamics (QCD) in suffciently strong magnetic fields and at moderate baryon number chemical potential carries a crystalline condensate of neutral pions: ...
    • Chiral soliton lattice phase in warm QCD 

      Brauner, Tomas; Kolesova, Helena; Yamamoto, Naoki (Peer reviewed; Journal article, 2021-11)
      We analyze the phase diagram of quantum chromodynamics at low-to-moderate temperature, baryon chemical potential and external magnetic field within chiral perturbation theory at next-to-leading order of the derivative ...
    • Competition of chiral soliton lattice and Abrikosov vortex lattice in QCD with isospin chemical potential 

      Grønli, Martin Spillum; Brauner, Tomas (Peer reviewed; Journal article, 2022-04)
      We investigate the thermodynamics of two-flavor quark matter in presence of nonzero isospin chemical potential and external magnetic field. It is known that at sufficiently high isospin chemical potential, charged pions ...
    • Dimensional reduction of the Standard Model coupled to a new singlet scalar field 

      Brauner, Tomas; Tenkanen, Tuomas; Tranberg, Anders; Vuorinen, Aleksi; Weir, David James (Journal article; Peer reviewed, 2017)
      We derive an effective dimensionally reduced theory for the Standard Model augmented by a real singlet scalar. We treat the singlet as a superheavy field and integrate it out, leaving an effective theory involving only the ...
    • Exceptional nonrelativistic effective field theories with enhanced symmetries 

      Brauner, Tomas (Peer reviewed; Journal article, 2021)
      We initiate the classification of nonrelativistic effective field theories (EFTs) for Nambu-Goldstone (NG) bosons, possessing a set of redundant, coordinate-dependent symmetries. Similarly to the relativistic case, such ...
    • Field theories with higher-group symmetry from composite currents 

      Brauner, Tomas (Peer reviewed; Journal article, 2021)
      Higher-form symmetries are associated with transformations that only act on extended objects, not on point particles. Typically, higher-form symmetries live alongside ordinary, point-particle (0-form), symmetries and they ...
    • Fractional Soft Limits of Scattering Amplitudes 

      Brauner, Tomas; Esposito, Angelo; Penco, Riccardo (Peer reviewed; Journal article, 2022)
      It is a common lore that the amplitude for a scattering process involving one soft Nambu-Goldstone boson should scale like an integer power of the soft momentum. We revisit this expectation by considering the 2 → 2 scattering ...
    • From Symmetries to Scattering Amplitudes: A Lie-algebraic categorisation of symmetry-breaking patterns that create enhanced soft limits for NG bosons 

      Bogers, Mark (PhD thesis UiS;, Doctoral thesis, 2022-11)
      The standard calculation of scattering amplitudes in quantum field theory is carried out using a perturbative expansion, that at successive orders contains an escalating number of terms to calculate. The amplitudes depend ...
    • Gauged Wess-Zumino terms for a general coset space 

      Brauner, Tomas; Kolesova, Helena (Peer reviewed; Journal article, 2019)
      The low-energy physics of systems with spontaneously broken continuous symmetry is dominated by the ensuing Nambu-Goldstone bosons. It has been known for half a century how to construct invariant Lagrangian densities for ...
    • Noether currents of locally equivalent symmetries 

      Brauner, Tomas (Peer reviewed; Journal article, 2020)
      Local symmetry transformations play an important role for establishing the existence and form of a conserved (Noether) current in systems with a global continuous symmetry. We explain how this fact leads to the existence ...
    • Nonrelativistic effective field theories with enhanced symmetries and soft behavior 

      Mojahed, Martin Aria; Brauner, Tomas (Peer reviewed; Journal article, 2022)
      We systematically explore the landscape of nonrelativistic effective field theories with a local S-matrix and enhanced symmetries and soft behavior. The exploration is carried out using both conventional quantum field ...
    • On-shell recursion relations for nonrelativistic effective field theories 

      Mojahed, Martin Aria; Brauner, Tomas (Peer reviewed; Journal article, 2021-10)
      We derive on-shell recursion relations for nonrelativistic effective field theories (EFTs) with enhanced soft limits. The recursion relations are illustrated through analytic calculation of tree-level scattering amplitudes ...
    • Scattering amplitudes of massive Nambu-Goldstone bosons 

      Brauner, Tomas; Jakobsen, Martin Fonnum (Journal article; Peer reviewed, 2018-01)
      Massive Nambu-Goldstone (mNG) bosons are quasiparticles the gap of which is determined exactly by symmetry. They appear whenever a symmetry is broken spontaneously in the ground state of a quantum many-body system and at ...
    • Thermodynamics of antiferromagnetic solids in magnetic fields 

      Brauner, Tomas; Hofmann, Christoph (Peer reviewed; Journal article, 2020)
      We analyze the thermodynamic properties of antiferromagnetic solids subjected to a combination of mutually orthogonal uniform magnetic and staggered fields. Low- temperature series for the pressure, order parameter and ...