Dark-energy properties of a spacetime-symmetry breaking cosmological solution -- late-time behaviour and phantom crossing

We investigate the late-time cosmological dynamics in a simple case of explicit spacetime-symmetry breaking. By expanding in a small symmetry-breaking coefficient we are able to write the Friedmann equations as $\Lambda$CDM + dynamical dark energy, which we show contains logarithmic dependence of the scale factor. We find that the dark energy equation of state displays divergences and phantom behaviour for certain values of the symmetry-breaking coefficient, where the Null Energy Condition is also broken. We also discuss the adiabatic sound speed of dark energy and compare the model to current constraints using the Chevallier-Polarski-Linder parametrisation.Comment: 7 pages, 4 figure

A 3+1 Decomposition of the Minimal Standard-Model Extension Gravitational Sector

The 3+1 (ADM) formulation of General Relativity is used in, for example, canonical quantum gravity and numerical relativity. Here we present a 3+1 decomposition of the minimal Standard-Model Extension gravity Lagrangian. By choosing the leaves of foliation to lie along a timelike vector field we write the theory in a form which will allow for comparison and matching to other gravity models.Comment: Presented at the Eighth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, May 12-16, 201

Toward Agent Programs with Circuit Semantics

New ideas are presented for computing and organizing actions for autonomous agents in dynamic environments-environments in which the agent's current situation cannot always be accurately discerned and in which the effects of actions cannot always be reliably predicted. The notion of 'circuit semantics' for programs based on 'teleo-reactive trees' is introduced. Program execution builds a combinational circuit which receives sensory inputs and controls actions. These formalisms embody a high degree of inherent conditionality and thus yield programs that are suitably reactive to their environments. At the same time, the actions computed by the programs are guided by the overall goals of the agent. The paper also speculates about how programs using these ideas could be automatically generated by artificial intelligence planning systems and adapted by learning methods

On the energy flow of λ\lambda in Ho\v{r}ava-Lifshitz cosmology

Ho\v{r}ava-Lifshitz gravity has been proposed as a ghost-free quantum gravity model candidate with an anisotropic UV-scaling between space and time. We present here a cosmological background analysis of two different formulations of the theory, with particular focus on the running of the parameter $\lambda$. Using a large dataset consisting of Cosmic Microwave Background data from {\it Planck}, Pantheon+ supernovae catalogue, SH0ES Cepheid variable stars, Baryon acoustic oscillations (BAO), Cosmic Chronometers, and gamma-ray bursts (GRB), we arrive at new bounds on the cosmological parameters, in particular $\lambda$, which describes deviation from classical general relativity. For the detailed balance scenario we arrive at the bound $\lambda=1.02726\pm0.00012$, and for beyond detailed balance the limit reads $\lambda=0.9949^{+0.0045}_{-0.0046}$. We also study the influence of different data sets and priors, and we find that removing low-redshift data generally moves $\lambda$ closer towards UV values, whilst simultaneously widening the error bars. In the detailed balance scenario, this effect is more noticeable, and $\lambda$ takes on values that are significantly below unity, which corresponds to the infrared limit of the theory.Comment: 16 pages, 2 tables, 1 figur

Mobile virtual worlds

This thesis examines the role of mobile access to virtual worlds in massively multiplayer online role playing games (MMORPG:s). Online gaming worlds have existed for decades, but ever since the smartphone has become more common, new interaction possibilities to these worlds have emerged. We have conducted a literature review to clarify existing gaps in the research community regarding mobile virtual worlds. Through this review, we have constructed a research model containing previously established motivation factors for MMORPG:s, interconnected with possible categories of how to improve the game experience with mobile features. An online survey on this topic was sent out to World of Warcraft players and the results show that many aspects of gameplay through mobile access could improve the gaming experience of virtual gaming worlds. The responses showed very mixed feelings about using many game features from the mobile phone, especially those that tie in with real life. An important finding among the results is the strong reluctance among the players to pay extra money for the addition of mobile access to the virtual world, and a low motivation to use synchronous gameplay features via a mobile computing device

Studies Into the Use of Non-linear Ultrasound to Detect Corroded Steel Plates Embedded in Concrete

In some nuclear power plants, the containment liners are embedded in concrete. The purpose of the containment liner is to minimize the risk of radioactive leakage by granting a leak-tight containment building. In the presence of flaws in the surrounding concrete, such as voids, or foreign objects embedded in the concrete, there is a risk that the liner plate might corrode. This could degrade the leak tightness of the containment building, leading to an increased risk of radioactive leakage. A project is being carried out at Lund University whose purpose is to assess the capability of non-linear ultrasound to detect corroded steel plates embedded in concrete. Second harmonic analysis has been used to determine if general corrosion induced an increase in acoustical non-linearity. This was done by inspecting a steel plate with varying grades of corrosion immersed in water. Results from this study indicated that severe corrosion increases the relative parameter of quadratic non-linearity ( Beta’). Beta' is given by the ratio between the second harmonic amplitude and the fundamental amplitudesquared. Building on this result, initial findings from modulation experiments on concrete cylinders with embedded steel plates with varying grades of corrosion are presented

Hur väl mäter en skördare?

Det finns två metoder för gallring, dels den stickvägsgående och dels den beståndsgående metoden. Beståndsgående skördare är oftast mindre och smalare än stickvägsgående, vilket underlättar vid beståndskörning. Problemet med beståndsgående gallringar kommer vid en eventuell andragallring, då en skördare av konventionell storlek normalt väljs. Intresset för de små skördarna har ökat, dels bland entreprenörer men också bland privata markägare. Ett behov av att undersöka ifall de små skördarna har förmåga att genomföra andragallring i de bestånd som gallrats med beståndsgående metod vid förstagallringen finns därmed. Ett steg är att säkerställa de små skördarnas förmåga att genomföra en korrekt mätning av virket. En stor och en liten skördare fick avverka två bestånd var, ett som representerade en förstagallring och ett som representerade en andragallring. Manuellt mätta stockar jämfördes med skördardatorns mätdata för längd- och diametermätningen. Oavsett bestånd mätte skördarna längre stockar än manuellt mätt längd. Den lilla skördarens träffprocent i längdmätningen var 96,4 procent och den storas 91,1 procent. Längdmätningsdifferensen var signifikant större på den lilla maskinen, vilket till viss del berodde på ett sämre resultat i det klena beståndet. Oavsett bestånd mätte skördarna stocken smalare än den manuellt mätta diametern. Diametermätningsdifferensen var signifikant större för den lilla maskinen och stockdiameter hade signifikant inverkan på mätningen. Träffprocenten vid diametermätningen var låg för båda maskinerna med en stor kalibreringspotential. En slutsats är att nyckeln för lyckad mätning i andragallring med små maskiner ligger i väl utvecklade rutiner för kalibrering av skördarna innan och under avverkning.There are two existing methods for thinning, the strip road-operated thinning and the stand-operated thinning. Harvesters used in stand-operated thinning’s are usually smaller and narrower than harvesters used in strip road-operated thinning’s. When stand-operated thinning method is chosen, there is a problem with the potential second thinning when a harvester of conventional size is used. There is a rising interest for the smaller harvesters, both among the entrepreneurs and the private landowners. Therefore, there is an upcoming need to investigate if the small harvesters have the ability to perform a second thinning in stands that have been thinned one time using the stand-operated thinning method. The ability to perform a correct measuring of the logs is one step in this investigation. One large and one small harvester felled trees in two stands, one representing a first thinning and one representing a second thinning. The harvesters data for the length and diameter measurement where compared with measurements taken manually. Regardless of stand, the harvesters measured longer logs then the manually measured length. The smaller harvester had a hit-percentage of 96.4 percent and the big one a hit-percentage of 91.1 percent. The difference between the machines length measurement and the manually was significantly larger for the smaller machine, which partly was depended on a poorer result in the slimmer stand. Regardless of stand, the harvesters measured diameter slimmer then the manually measured diameter. The difference between the machines diameter measurement and the manually was significantly larger for the small machine and log diameter had a significant impact on the measurement. The hit-percentage of the diameter measurement was low for both machines with a large potential in calibration. A conclusion is that a key for a successful measuring in second thinning´s is well-developed routines for calibration for the harvesters before and during the harvest