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Critical properties of the valence-bond-solid transition in lattice quantum electrodynamics
No full textElucidating the phase diagram of lattice gauge theories with fermionic matter in 2+1 dimensions has become a problem of considerable interest in recent years, motivated by physical problems ranging from chiral symmetry breaking in high-energy physics to fractionalized phases of strongly correlated materials in condensed matter physics. For a sufficiently large number of flavors of four-component Dirac fermions, recent sign-problem-free quantum Monte Carlo studies of lattice quantum electrodynamics (QED) on the square lattice have found evidence for a continuous quantum phase transition between a power-law correlated conformal QED phase and a confining valence-bond-solid phase with spontaneously broken point-group symmetries. The critical continuum theory of this transition was shown to be the QED-Gross-Neveu model, equivalent to the gauged Nambu-Jona-Lasinio model, and critical exponents were computed to first order in the large- expansion and the expansion. We extend these studies by computing critical exponents to second order in the large- expansion and to four-loop order in the expansion below four spacetime dimensions. In the latter context, we also explicitly demonstrate that the discrete symmetry of the valence-bond-solid order parameter is dynamically enlarged to a continuous symmetry at criticality for all values of
Gravitational Wave Production right after Primordial Black Hole Evaporation
No full textWe discuss the footprint of evaporation of primordial black holes (PBHs) on stochastic gravitational waves (GWs) induced by scalar perturbations. We consider the case where PBHs once dominate the Universe but eventually evaporate before the big bang nucleosynthesis. The reheating through the PBH evaporation could end with a sudden change in the equation of state of the Universe compared to the conventional reheating caused by particle decay. We show that this 'sudden reheating' by the PBH evaporation enhances the induced GWs, whose amount depends on the length of the PBH-dominated era and the width of the PBH mass function. We explore the possibility to constrain the primordial abundance of the evaporating PBHs by observing the induced GWs. We find that the abundance parameter for PBHs can be constrained by future GW observations if the width of the mass function is smaller than about a hundredth of the mass
Toward a Plasma-based Accelerator at High Beam Energy with High Beam Charge and High Beam Quality
No full textFrom plasma-wakefield acceleration as a physics experiment toward a plasma-based accelerator as a user facility, the beam physics issues remaining to be solved are still numerous. Providing beams with high energy, charge, and quality simultaneously, not only within the plasma but also at the user doorstep itself, is the main concern. Despite its tremendous efficiency in particle acceleration, the wakefield displays a complex 3D profile which, associated to the beam-loading field induced by the accelerated beam itself, makes the acceleration of high charge to high energy often incompatible with high beam quality. Beam extraction from the plasma without quality degradation for a transfer either to the next plasma stage or to the user application is another difficulty to consider. This article presents the substantial studies carried out and the different innovative methods employed for tackling all these different issues. Efforts focused on achieving the challenging beam parameters targeted by the EuPRAXIA accelerator facility project. The lessons learned at the end of these in-depth simulations and optimizations are highlighted. The sensitivity to different error sources is also estimated to point out the critical components of such an accelerator. Finally, the needs in terms of laser and plasma parameters are provided
Integrability in N = 1 Gauge Theories
No full textIn this thesis we investigate two questions that shed new light on fundamentalproperties of supersymmetric gauge theories.Our first topic deals with the question, which implications results for N = 4 Super-Yang-Mills have on theories with less symmetry. Specifically we conjecture that thedilatation operator in the SU(2, 1|1) sector of any N = 1 superconformal gauge theorycan be found from the one for N = 4 Super-Yang-Mills by a redefinition of the couplingconstant. This implies its integrability. We prove this conjecture perturbatively upto three loops for the vacuum of this sector and discuss generalizations to the wholesector.Our second investigation concerns the protected spectrum of N = 2 superconformalQCD. It is much richer than naively expected. In particular it contains states witharbitrarily large spin, which has been shown by means of the superconformal index.However their form was as of yet unknown. We present an algorithm that explicitlyconstructs these states in terms of the fundamental fields of the theory
No go for a flow
No full textWe prove that a very large class of general Argyres-Douglas theories cannot admit a UV lagrangian which flows to them via the Maruyoshi-Song supersymmetry enhancement mechanism. We do so by developing a computer program which brute-force lists, for any given 4d superconformal theory , all possible UV candidate superconformal lagrangians satisfying some necessary criteria for the supersymmetry enhancement to happen. We argue that this is enough evidence to conjecture that it is impossible, in general, to find new examples of Maruyoshi-Song lagrangians for generalized Argyres-Douglas theories. All lagrangians already known are, on the other hand, recovered and confirmed in our scan. Finally, we also develop another program to compute efficiently Coulomb branch spectrum, masses, couplings and central charges for Argyres-Douglas theories of arbitrarily high rank
Charged multi-hadron systems in lattice QCD+QED
No full textSystems with the quantum numbers of up to twelve charged and neutral pseudoscalar mesons, as well as one-, two-, and three-nucleon systems, are studied using dynamical lattice quantum chromodynamics and quantum electrodynamics (QCD+QED) calculations and effective field theory. QED effects on hadronic interactions are determined by comparing systems of charged and neutral hadrons after tuning the quark masses to remove strong isospin breaking effects. A non-relativistic effective field theory, which perturbatively includes finite-volume Coulomb effects, is analyzed for systems of multiple charged hadrons and found to accurately reproduce the lattice QCD+QED results. QED effects on charged multi-hadron systems beyond Coulomb photon exchange are determined by comparing the two- and three-body interaction parameters extracted from the lattice QCD+QED results for charged and neutral multi-hadron systems
Fingerprint matching of beyond-WIMP dark matter: neural network approach
No full textImproving observation of galactic-scale structure provide important clues to dark matter properties. While weakly interacting massive particles (WIMPs) provide cold dark matter on galactic scales, beyond-WIMP candidates suppress the galactic-scale structure formation. Nevertheless, directly constraining microscopic model parameters from observations involves an interdisciplinary and time-consuming procedure. In practice, some parametrizations of the linear matter power spectrum are introduced. The particle physics community calculates the linear matter power spectrum for a given model parameter set, while the astrophysics community places the constraint on the power spectrum parameters. If maps between the model parameters and the power spectrum parameters and maps between the power spectrum parameters and the likelihood (or observables) are shared among the two communities, they are very useful for both communities, e.g., making a constraint plot of the model parameter space. As suggested in the literature, however, it is necessary to introduce multiple parameters to precisely describe the linear matter power spectrum in a wide range of beyond-WIMP models. It challenges us to express and share the non-linear maps between multiple parameters. In this work, we propose utilizing the neural network technique to this end. The neural network technique is known to automatically express and efficiently share non-linear maps, although it is not as simple as analytic fitting formulas if available. To demonstrate how to work with a concrete example, we consider a simplified model of light feebly interacting massive particles and simple observables for galactic-scale structure. We also reveal the obtained neural networks through the arXiv website
Axion-electron decoupling in nucleophobic axion models
No full textThe strongest upper bounds on the axion mass come from astrophysical observations like the neutrino burst duration of SN1987A, which depends on the axion couplings to nucleons, or the white-dwarf cooling rates and red-giant evolution, which involve the axion-electron coupling. It has been recently argued that in variants of Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) models with generation-dependent Peccei-Quinn charges an approximate axion-nucleon decoupling can occur, strongly relaxing the SN1987A bound. However, as in standard DFSZ models, the axion remains in general coupled to electrons, unless an ad hoc cancellation is engineered. Here we show that axion-electron decoupling can be implemented without extra tunings in DFSZ-like models with three Higgs doublets. Remarkably, the numerical value of the quark mass ratio mu/md∼1/2 is crucial to open up this possibility
Production of baryons in proton-proton and lead-lead collisions at 5.02 TeV
No full textThe transverse momentum ( pT ) spectra of inclusively produced Λc+ baryons are measured via the exclusive decay channel Λc+→pK−π+ using the CMS detector at the LHC. Spectra are measured as a function of transverse momentum in proton-proton ( pp ) and lead-lead (PbPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The measurement is performed within the Λc+ rapidity interval |y|<1 in the pT range of 5–20 GeV/c in pp and 10–20 GeV/c in PbPb collisions. The observed yields of Λc+ for pT of 10–20 GeV/c suggest a suppression in central PbPb collisions compared to pp collisions scaled by the number of nucleon-nucleon (NN) interactions. The Λc+/D0 production ratio in pp collisions is compared to theoretical models. In PbPb collisions, this ratio is consistent with the result from pp collisions in their common pT range
Hot deformation of Mg-Y-Zn alloy with a low content of the LPSO phase studied by in-situ synchrotron radiation diffraction
No full textThe compressive deformation behavior of the extruded WZ42 (Mg98.5Y1Zn0.5 in at.%) magnesium alloy containing a low amount of long-period stacking ordered (LPSO) phase was studied by in-situ synchrotron radiation diffraction technique. Tests were conducted at temperatures between room temperature and 350 °C. Detailed microstructure investigation was provided by scanning electron microscopy, particularly the backscattered electron imaging and electron backscatter diffraction technique. The results show that twinning lost its dominance and kinking of the LPSO phase became more pronounced with increasing deformation temperature. No cracks of the LPSO phase and no debonding r at the interface between the LPSO phase and the Mg matrix were observed at temperatures above 200 °C. At 350 °C, the LPSO phase lost its strengthening effect and the deformation of the alloy was mainly realized by the dynamic recrystallization of the Mg matrix