Search results for "renormalization"
showing 10 items of 470 documents
Towards gauge coupling unification in left-right symmetric SU(3)c×SU(3)L×SU(3)R×U(1)X theories
2017
We consider the possibility of gauge coupling unification within the simplest realizations of the $\mathrm{SU}(3{)}_{\mathrm{c}}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(3{)}_{\mathrm{L}}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(3{)}_{\mathrm{R}}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{\mathrm{X}}$ gauge theory. We present a first exploration of the renormalization group equations governing the ``bottom-up'' evolution of the gauge couplings in a generic model with free normalization for the generators. Interestingly, we find that for a $\mathrm{SU}(3{)}_{\mathrm{c}}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(3{)}_{\mathrm{L}}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(…
gg→HH : Combined uncertainties
2021
In this paper we discuss the combination of the usual renormalization and factorization scale uncertainties of Higgs-pair production via gluon fusion with the novel uncertainties originating from the scheme and scale choice of the virtual top mass. Moreover, we address the uncertainties related to the top-mass definition for different values of the trilinear Higgs coupling and their combination with the other uncertainties.
The liquid-solid transition of hard discs: first-order transition or Kosterlitz-Thouless-Halperin-Nelson-Young scenario?
2002
We consider the question of whether a two-dimensional hard-disc fluid has a first-order transition from the liquid state to the solid state as in the three-dimensional melting-crystallization transition or whether one has two subsequent continuous transitions, from the liquid to the hexatic phase and then to the solid phase, as proposed by Kosterlitz, Thouless, Halperin, Nelson and Young (KTHNY). Monte Carlo (MC) simulations of the fluid that study the growth of the bond orientational correlation length, and of the crystal are discussed. The emphasis is on a recent consistency test of the KTHNY renormalization group (RG) scenario, where MC simulations are used to estimate the bare elastic c…
B-parameters for ΔS=2 supersymmetric operators
1998
We present a calculation of the matrix elements of the most general set of DeltaS=2 dimension-six four-fermion operators. The values of the matrix elements are given in terms of the corresponding B-parameters. Our results can be used in many phenomenological applications, since the operators considered here give important contributions to K^0--K^0bar mixing in several extensions of the Standard Model (supersymmetry, left-right symmetric models, multi-Higgs models etc.). The determination of the matrix elements improves the accuracy of the phenomenological analyses intended to put bounds on basic parameters of the different models, as for example the pattern of the sfermion mass matrices. Th…
Mass and width of the Delta resonance using complex-mass renormalization
2016
The pole mass and width of the Delta resonance are calculated in the relativistic chiral effective field theory approach. We choose a systematic power-counting procedure by applying the complex-mass scheme (CMS).
Stripe formation in doped Hubbard ladders
2004
We investigate the formation of stripes in $7\chunks \times 6$ Hubbard ladders with $4\chunks$ holes doped away from half filling using the density-matrix renormalization group (DMRG) method. A parallelized code allows us to keep enough density-matrix eigenstates (up to $m=8000$) and to study sufficiently large systems (with up to $7\chunks = 21$ rungs) to extrapolate the stripe amplitude to the limits of vanishing DMRG truncation error and infinitely long ladders. Our work gives strong evidence that stripes exist in the ground state for strong coupling ($U=12t$) but that the structures found in the hole density at weaker coupling ($U=3t$) are an artifact of the DMRG approach.
Effective Field Theory
2015
Effective field theories (EFTs) are a highly important topic in Quantum Field Theory. Here we are going to shortly present some important highlights as well as the renormalization group equations for the Wilson coefficients. Afterwards we shall focus on one illustrative example and present the \(\textit{matching}\) procedure at the one-loop level. The infrared behaviour of EFTs is also covered with this example.
Temperature and doping dependence of normal state spectral properties in a two-orbital model for ferropnictides
2016
Using a second-order perturbative Green's functions approach we determined the normal state single-particle spectral function $A(\vec{k},\omega)$ employing a minimal effective model for iron-based superconductors. The microscopic model, used before to study magnetic fluctuations and superconducting properties, includes the two effective tight-binding bands proposed by S.Raghu et al. [Phys. Rev. B 77, 220503 (R) (2008)], and intra- and inter-orbital local electronic correlations, related to the Fe-3d orbitals. Here, we focus on the study of normal state electronic properties, in particular the temperature and doping dependence of the total density of states, $A(\omega)$, and of $A(\vec{k},\o…
Spectral Analysis of Nonrelativistic Quantum Electrodynamics
2001
I review the research results on spectral properties of atoms and molecules coupled to the quantized electromagnetic field or on simplified models of such systems obtained during the past decade. My main focus is on the results I have obtained in collaboration with Jurg Frohlich and Israel Michael Sigal [8, 9, 10, 11, 12, 13].
The renormalized electron mass in non-relativistic quantum electrodynamics
2007
This work addresses the problem of infrared mass renormalization for a scalar electron in a translation-invariant model of non-relativistic QED. We assume that the interaction of the electron with the quantized electromagnetic field comprises a fixed ultraviolet regularization and an infrared regularization parametrized by $\sigma>0$. For the value $p=0$ of the conserved total momentum of electron and photon field, bounds on the renormalized mass are established which are uniform in $\sigma\to0$, and the existence of a ground state is proved. For $|p|>0$ sufficiently small, bounds on the renormalized mass are derived for any fixed $\sigma>0$. A key ingredient of our proofs is the operator-t…