Search results for "REGULARIZATION"
showing 10 items of 189 documents
Deconvolution of the spectral line profiles for the plasma temperature estimation
2010
Abstract The Hg 253.7 nm spectral line profiles, emitted from the mercury–argon high-frequency electrodeless discharge lamps (HFEDL) have been measured by means of a high-resolution scanning Fabry–Perrot interferometer at the mercury cold spot temperature value at 20 °C, different discharge current and buffer gas values. The deconvolution procedure by means of the Tikhonov's regularization method was performed to obtain the real spectral line shape. The influence of the instrumental function and absorption, real width of the Hg 253.7 nm resonance line and temperature of the radiating atoms are obtained. The results were compared with the results of the nonlinear multiparameter mathematical …
Renormalization of the 1S0 One-Pion-Exchange NN Interaction in Presence of Derivative Contact Interactions
2003
We use standard distorted wave theory techniques and dimensional regularization to find out solutions of the nucleon-nucleon Lippman--Schwinger equation with a kernel determined by the Weinberg's next-to-leading potential, which consists of one--pion exchange and additional contact terms with derivatives. Though for simplicity, we restrict the discussion to the $^1S_0$ channel and to contact terms containing up to two derivatives, the generalization to higher waves and/or number of derivatives is straightforward. The undetermined low energy constants emerging out of the renormalization procedure are fitted to data.
Effective theory for low-energy nuclear energy density functionals
2012
We introduce a new class of effective interactions to be used within the energy-density-functional approaches. They are based on regularized zero-range interactions and constitute a consistent application of the effective-theory methodology to low-energy phenomena in nuclei. They allow for defining the order of expansion in terms of the order of derivatives acting on the finite-range potential. Numerical calculations show a rapid convergence of the expansion and independence of results of the regularization scale.
Renormalization of relativistic baryon chiral perturbation theory and power counting
2003
We discuss a renormalization scheme for relativistic baryon chiral perturbation theory which provides a simple and consistent power counting for renormalized diagrams. The method involves finite subtractions of dimensionally regularized diagrams beyond the standard $\bar{\rm MS}$ scheme of chiral perturbation theory to remove contributions violating the power counting. This is achieved by a suitable renormalization of the parameters of the most general effective Lagrangian. In addition to simplicity our method has the benefit that it can be easily applied to multiloop diagrams. As an application we discuss the mass and the scalar form factor of the nucleon and compare the results with the e…
S-waveKK*interactions in a finite volume and thef1(1285)
2015
Lattice QCD simulations provide a promising way to disentangle different interpretations of hadronic resonances, which might be of particular relevance to understand the nature of the so-called XY Z particles. Recent studies have shown that in addition to the well-established naive quark model picture, the axial-vector meson f1(1285) can also be understood as a dynamically generated state built upon the KK ∗ interaction. In this work, we calculate the energy levels of the KK ∗ system in the f1(1285) channel in finite volume using the chiral unitary approach. We propose to calculate the loop function in the dimensional regularization scheme, which is equivalent to the hybrid approach adopted…
ρρinteraction in the hidden gauge formalism and thef0(1370)andf2(1270)resonances
2008
We have studied the interaction of vector mesons within the hidden gauge formalism and applied it to the particular case of the $\ensuremath{\rho}\ensuremath{\rho}$ interaction. We find a strong attraction in the isospin, spin channels $I$, $S=0$, 0 and 0, 2, which is enough to bind the $\ensuremath{\rho}\ensuremath{\rho}$ system. We also find that the attraction in the $I$, $S=0$, 2 channel is much stronger than in the 0, 0 case. The states develop a width when the $\ensuremath{\rho}$ mass distribution is considered, and particularly when the $\ensuremath{\pi}\ensuremath{\pi}$ decay channel is turned on. Using a regularization scheme with cutoffs of natural size, we obtain results in fair …
Chiral corrections to the 1 −+ exotic meson mass
2016
We first construct the effective chiral Lagrangians for the $1^{-+}$ exotic mesons. With the infrared regularization scheme, we derive the one-loop infrared singular chiral corrections to the $\pi_1(1600)$ mass explicitly. We investigate the variation of the different chiral corrections with the pion mass under two schemes. Hopefully, the explicit non-analytical chiral structures will be helpful to the chiral extrapolation of the lattice data from the dynamical lattice QCD simulation of either the exotic light hybrid meson or tetraquark state.
Can power corrections be reliably computed in models with extra dimensions?
2003
We critically revisit the issue of power-law running in models with extra dimensions. The analysis is carried out in the context of a higher-dimensional extension of QED, with the extra dimensions compactified on a torus. It is shown that a naive $\beta$ function, which simply counts the number of modes, depends crucially on the way the thresholds of the Kaluza-Klein modes are crossed. To solve these ambiguities we turn to the vacuum polarization, which, due to its special unitarity properties, guarantees the physical decoupling of the heavy modes. This latter quantity, calculated in the context of dimensional regularization, is used for connecting the low energy gauge coupling with the cou…
Pinch technique at two loops: The case of massless Yang-Mills theories
2000
The generalization of the pinch technique beyond one loop is presented. It is shown that the crucial physical principles of gauge-invariance, unitarity, and gauge-fixing-parameter independence single out at two loops exactly the same algorithm which has been used to define the pinch technique at one loop, without any additional assumptions. The two-loop construction of the pinch technique gluon self-energy, and quark-gluon vertex are carried out in detail for the case of mass-less Yang-Mills theories, such as perturbative QCD. We present two different but complementary derivations. First we carry out the construction by directly rearranging two-loop diagrams. The analysis reveals that, quit…
EXTRACTION OF INFRARED DIVERGENCES IN THE DIMENSIONAL REGULARIZED TWO-LOOP LADDER GRAPH
1994
We consider the evaluation of the fundamental scalar integral in the on-shell two-loop ladder graph with different external masses and arbitrary transfer momentum. A method for cleanly extracting the infrared divergences in the Feynman parameter integrals using dimensional regularization is presented, and we analyze one of the finite part contributions to this integral.