Naturalness

About: Naturalness is a research topic. Over the lifetime, 1305 publications have been published within this topic receiving 31737 citations.

Neutrino mass implications for muon decay parameters

Abstract: We use the scale of neutrino mass and naturalness considerations to obtain model-independent expectations for the magnitude of possible contributions to muon decay Michel parameters from new physics above the electroweak symmetry-breaking scale. Focusing on Dirac neutrinos, we obtain a complete basis of dimension four and dimension six effective operators that are invariant under the gauge symmetry of the standard model and that contribute to both muon decay and neutrino mass. We show that—in the absence of fine tuning—the most stringent neutrino-mass naturalness bounds on chirality-changing vector operators relevant to muon decay arise from one-loop operator mixing. The bounds we obtain on their contributions to the Michel parameters are 2 orders of magnitude stronger than bounds previously obtained in the literature. In addition, we analyze the implications of one-loop matching considerations and find that the expectations for the size of various scalar and tensor contributions to the Michel parameters are considerably smaller than derived from previous estimates of two-loop operator mixing. We also show, however, that there exist gauge-invariant operators that generate scalar and tensor contributions to muon decay but whose flavor structure allows them to evade neutrino-mass naturalness bounds. We discuss the implications of our analysis for the interpretation of muon-decay experiments.

Low-mass neutralino dark matter in supergravity scenarios: phenomenology and naturalness

Abstract: The latest experimental results from the LHC and dark matter (DM) searches suggest that the parameter space allowed in supersymmetric theories is subject to strong reductions. These bounds are especially constraining for scenarios entailing light DM particles. Previous studies have shown that light neutralino DM in the Minimal Supersymmetric Standard Model (MSSM), with parameters defined at the electroweak scale, is still viable when the low energy spectrum of the model features light sleptons, in which case, the relic density constraint can be fulfilled. In view of this, we have investigated the viability of light neutralinos as DM candidates in the MSSM, with parameters defined at the grand unification scale. We have analysed the optimal choices of non-universalities in the soft supersymmetry-breaking parameters for both, gauginos and scalars, in order to avoid the stringent experimental constraints. We show that light neutralinos, with a mass as low as 25 GeV, are viable in supergravity scenarios if the gaugino mass parameters at high energy are very non universal, while the scalar masses can remain of the same order. These scenarios typically predict a very small cross section of neutralinos off protons and neutrons, thereby being very challenging for direct detection experiments. However, a potential detection of smuons and selectrons at the LHC, together with a hypothetical discovery of a gamma-ray signal from neutralino annihilations in dwarf spheroidal galaxies could shed light on this kind of solutions. Finally, we have investigated the naturalness of these scenarios, taking into account all the potential sources of tuning. Besides the electroweak fine-tuning, we have found that the tuning to reproduce the correct DM relic abundance and that to match the measured Higgs mass can also be important when estimating the total degree of naturalness.

Methodology for establishing the degree of naturalness of forest stands.

Abstract: Forest stands naturalness degree represents the real tree species composition comparison with the tree species on natural vegetation level - It means forest typology units. The natural tree species composition is derived from Typological System of UHUL (Forest Management Institute). The degree of naturalness of forests is one of the attributes for the assessment of the ecological stability of forests, whilst the broader basis for analysis of sustainable development of the territory.The real tree species composition comes from the forest management planes database and the natural potential vegetation one from typological sites units (forest site complex). Forests types complex is a higher unit of this system hierarchy.The solution based on comparison of the real species composition with natural potential vegetation, e.g. forest stands naturalness degree, is to be used in the ecosystem platform way. The preparation of entry data, e.g. allocation of structured stand type code to the real and natural species composition precedes the analysis itself. Then follows the tree species index calculation which means the final sum of tree index present and any absent species. This index presents the difference between the real tree condition and the model one. It is used entirely original concept algorithm of structured stand types.This algorithm allows for the application computer technology and process so the range from forest stand group of up to the large territory (CZ).The naturalness degree classification is defined on 0-6 levels, from zero degree for introduced species, 3rd degree for cultural forests, to 6th degree for those with natural tree composition. The limited criterion is the stand naturalness degree which should be on 4th level and above.This method is for 15 years of application not only in the works of forestry sites typology completely worked.

Nonrelativistic Naturalness in Aristotelian Quantum Field Theories

Abstract: Author(s): Yan, Ziqi | Advisor(s): Horava, Petr | Abstract: Some of the most fundamental questions in theoretical physics can be formulated as puzzles of naturalness, such as the cosmological constant problem and the Higgs mass hierarchy problem. In condensed matter physics, the interpretation of the linear scaling of resistivity with temperature in the strange metal phase of high-temperature superconductors also arises as a naturalness puzzle. In this thesis, we explore the landscape of naturalness in nonrelativistic quantum field theories that exhibit anisotropic scaling in space and time. Such theories are referred to as the ``Aristotelian quantum field theories." In the simple case with scalars, we find that the constant shift symmetry is extended to a shift by a polynomial in spatial coordinates, which protects the technical naturalness of modes with a higher order dispersion. This discovery leads to a generalization of the relativistic Coleman-Hohenberg-Mermin-Wagner (CHMW) theorem to multicritical cases in lower critical dimension. By breaking the polynomial shift symmetries in a hierarchy, we find novel cascading phenomena with large natural hierarchies between the scales at which the values of z change, leading to an evasion of the "no-go" consequences of the relativistic CHMW theorem. Based on these formal developments, we propose potential applications both to the Higgs mass hierarchy problem and to the problem of linear resistivity in strange metals. Finally, encouraged by these nonrelativistic surprises that already arise in simple systems with scalars, we move on to more complicated systems with gauge symmetries. We study the quantization of Horava gravity in 2+1 dimensions and compute the anomalous dimension of the cosmological constant at one loop. However, nonrelativistic naturalness in gravity is still largely unexplored. Whether or not such nonrelativsitic twists have any implications for important naturalness puzzles, such as the cosmological constant problem, remains as an intriguing question.

Do Firm Cues Impact Product Perceptions? When Small is Natural

Abstract: Firms of varying size can produce the same product. Do consumers make inferences about products based on firm size? We focus on perceptions of product naturalness and show, in four studies, that products made by smaller firms are perceived to be more natural — whether they are directly experienced (study 1) or seen in ads (study 2). Additionally, we show that the association of firm size and naturalness is held non=consciously (study 3), and also consciously (study 2); and that it impacts purchase intention (studies 2 and 4). Our research has many implications for firms conveying product naturalness. Importantly, it highlights the need to explore possible associations between firm characteristics and product perceptions.