119218745
Effective potential and vacuum stability
By following previous work on this subject, we investigate the issue of the instability of the electroweak vacuum against the top loop corrections by performing an accurate analysis of a Higgs–Yukawa model. We find that when the physical cutoff is properly implemented in the theory the potential does not exhibit any instability. Moreover, contrary to recent claims, we show that this instability cannot be understood in terms of the very insightful work of Wu and Weinberg on the non-convexity of the one-loop effective potential of a scalar theory. Some of the theoretical and phenomenological consequences of our results are briefly discussed.
118725527
STRUCTURE OF THE BROKEN PHASE OF THE SINE-GORDON MODEL USING FUNCTIONAL RENORMALIZATION
We study in this paper the sine-Gordon model using functional renormalization group at local potential approximation using different renormalization group (RG) schemes. In d = 2, using Wegner–Houghton RG we demonstrate that the location of the phase boundary is entirely driven by the relative position to the Coleman fixed point even for strongly coupled bare theories. We show the existence of a set of IR fixed points in the broken phase that are reached independently of the bare coupling. The bad convergence of the Fourier series in the broken phase is discussed and we demonstrate that these fixed points can be found only using a global resolution of the effective potential. We then introduce the methodology for the use of average action method where the regulator breaks periodicity and show that it provides the same conclusions for various regulators. The behavior of the model is then discussed in d≠2 and the absence of the previous fixed points is interpreted.
119227355
Generating the mass gap of the sine-Gordon model
We discuss in this study the possibility of finding a finite mass gap in the broken phase of the sine-Gordon model in $d=2$ using the functional flows. We demonstrate that the signal of the presence of massive excitations, a finite positively-curved {\em blocked} potential around its minima, is recovered only in our treatment. The usual results based on the flow of the Fourier expansion of the {\em blocked} action are then shown to actually fit a singularity.
32573284
Island of rare Earth nuclei with tetrahedral and octahedral symmetries: possible experimental evidence.
Calculations using realistic mean-field methods suggest the existence of nuclear shapes with tetrahedral Td and/or octahedral Oh symmetries sometimes at only a few hundreds of keV above the ground states in some rare earth nuclei around 156Gd and 160Yb. The underlying single-particle spectra manifest exotic fourfold rather than Kramers's twofold degeneracies. The associated shell gaps are very strong, leading to a new form of shape coexistence in many rare earth nuclei. We present possible experimental evidence of the new symmetries based on the published experimental results--although an unambiguous confirmation will require dedicated experiments.
125580973
An RG study of models with spontaneous symmetry breaking
14538104
NUCLEI WITH TETRAHEDRAL SYMMETRY
We discuss a point-group-theory based method of searching for new regions of nuclear stability. We illustrate the related strategy with realistic calculations employing the tetrahedral and the octahedral point groups. In particular, several nuclei in the Rare Earth region appear as excellent candidates to study the new mechanism.