An Alternative to the Schwarzschild solution of GTR

The Schwarzschild solution (Schwarzschild, 1915/16) to Einstein’s General Theory of Relativity (GTR) is accepted in theoretical physics as the unique solution to GTR for a central-mass system. In this paper I propose an alternative solution to GTR, and argue it is both logically consistent and empirically realistic as a theory of gravity. This solution is here called K-gravity. The introduction explains the basic concept. The central sections go through the technical detail, defining the basic solution for the geometric tensor, the Christoffel symbols, Ricci tensor, Ricci scalar, Einstein tensor, stress-energy tensor and density-pressure for the system. The density is integrated, and some consistency properties are demonstrated. A notable feature is the disappearance of the event horizon singularity, i.e. there are no black holes. So far this is for a single central mass. A generalization of the solution for multiple masses is then proposed. This is required to support K-gravity as a viable general interpretation of gravity. Then the question of empirical tests is discussed. It is argued that current observational data is almost but not quite sufficient to verify or falsify K-gravity. The Pioneer spacecraft trajectory data is of particular interest, as this is capable of providing a test; but the data (which originally showed anomalies that match K-gravity) is now uncertain. A new and very practical experiment is proposed to settle the matter. This would provide a novel test of GTR, and a novel test of the cause of the Pioneer anomalies. In conclusion, K-gravity has extensive ramifications for gravitational physics and for the philosophy of GTR and space-time

Twitter Bot Detection

In this thesis, I explore the identification of non-human Twitter users. I am interested in classifying users by behavior into the categories of either bot or human. My goal in this research is to find an accurate and efficient means of identifying and segregating non-human Twitter users from their human counterparts. I use a two-stage data collection process to collect Twitter users suspected of being a bot and then obtain a majority vote on the suspected users to validate the suspicion. I gather, on average, 1000 tweets per user, on which I calculate 40 features characterizing the user. I explore the effectiveness of three different methods to most accurately classify users as either a bot or a human based on these features. The results of this work show that bots can be classified efficiently and with a high degree of accuracy. I show that certain features play a larger role in the classification process than others. The applications of Twitter bot identification include: (i) protecting users from malicious content (ii) spam filtering, and (iii) bot removal from Twitter data for other research

College admissions as a market design problem

Opiskelijavalintojen suunnittelu on herättänyt Suomessa paljon keskustelua, kun viimeaikaiset poliittiset päätökset ovat muuttaneet valintajärjestelmää keskitetympään suuntaan. Jotkut antaisivat korkeakoulujen itse päättää opiskelijavalinnoistaan, kun taas toiset uskovat keskitetyn ja ylioppilastutkinnon arvosanoja hyödyntävän valintajärjestelmän olevan entistä, hajautettua järjestelmää kustannustehokkaampi. Tarkastellen sekä keskitettyjen että hajautettujen pariutumismarkkinoiden teoriaa että myös kouluvalintoja ja pääsykokeita koskevaa empiiristä kirjallisuutta, tämä tutkielma pyrkii kuvaamaan niitä lukuisia tekijöitä, joita politiikantekijän täytyy huomioida opiskelijavalintoja kehittäessä. Todellisten mekanismien suunnitteluun hyvin soveltuvana kaksisuuntaisten pariutumismarkkinoiden kirjallisuuteen perehdytään syvällisesti. Niin sanottu student-proposing deferred acceptance –algoritmi osoittautuu parhaaksi valinnaksi, jos politiikantekijä kokee erityisen tärkeäksi, että mekanismi kannustaa hakijoita totuudenpuhumiseen, ja toisaalta valintakriteerinä käytettävää pisteytystä noudatetaan. Näin ainakin, jos korkeakoulujen ei uskota manipuloivan mekanismia. Käytännön mekanismit kuitenkin usein jättävät hakijoille joitain kannustimia raportoida todellisista eroavia preferensseja, hakijat saattavat raportoida epätosia preferensseja itselleen epäedullisesti, ja student-proposing deferred acceptance –algoritmissakin kaikkien mahdollisten hakukohteiden asettaminen preferenssijärjestykseen on vain heikosti dominanttia. Siksi ilmoitettuja preferenssejä ei tulisi ajatella suoraksi todistusaineistoksi hakijoiden preferensseistä. Korkeakouluille yhteiset pääsykokeet ylioppilastutkinnon muodossa voivat olla hajautettua järjestelmää kustannustehokkaampia, kun korkeakoulujen ei tarvitse kuluttaa resursseja erillisten pääsykokeiden järjestämiseen. Opiskelijoilla on kuitenkin sitten korkeammat kannustimet menestyä ylioppilaskokeissa, ja on jo näyttöä siitä, että ylioppilastutkinnon arvosanoja pyritään korottamaan entistä enemmän. Kokonaisvaikutus kustannuksiin jää siis epävarmaksi empiiriseksi kysymykseksi. Valmennuskurssien tärkeys vähentynee, mikä säästää yhteiskunnan resursseja ja lisää sosioekonomista tasa-arvoa. Toisaalta aikaisemmin elämässä tehtyjen valintojen merkitys korostuu, mikä saattaa heikentää sosioekonomista tasa-arvoa. Ylioppilastutkinnon tärkeyden korostuminen parantaa kannustimia ahkeraan opiskeluun jo lukio-opintojen aikana, minkä politiikantekijä voi nähdä hyödylliseksi. Vaikka yhteisiin pääsykokeisiin perustuva valintajärjestelmä parantaa huomattavasti opiskelijan mahdollisuuksia tulla valituksi toissijaiseen hakukohteeseen tultuaan hylätyksi ensisijaisesta hakukohteesta, jää empiiriseksi kysymykseksi, kuinka paljolti tämä vähentää uudelleenhakemista kilpailtuihin opiskelupaikkoihin. Tiettyihin korkeakouluihin kohdistuva ylikysyntä on suora seuraus hakijoiden preferensseistä, eikä ratkaistavissa millään mekanismilla, mikä antaa korkean arvon hakijoiden preferenssien tyydyttämiselle.The design of college admissions has been a heatedly discussed topic in Finland, as recent government initiatives have led to a more centralized system. Some argue for letting colleges decide on their admissions procedures, while others believe that a centralized matchmaking procedure with priorities determined by the matriculation examination would be more cost-effective. This thesis aims to characterize various factors that the policy maker must take into account when designing a college admissions procedure, in light of existing theoretical research on both centralized and decentralized matching markets and empirical studies on social determinants of college choice and the capacity of entrance examinations to elicit information on student ability and motivation. The two-sided matching literature is discussed extensively because of its usefulness for designing centralized clearinghouses for matching markets. The student-proposing deferred acceptance algorithm emerges as the best choice for a policy maker who regards strategy-proofness and respecting of priorities as especially important, at least if manipulation by colleges is implausible. However, strategy-proofness is fragile in practical applications, applicants may try to manipulate also strategy-proof mechanisms and reporting the whole preference relation is still only weakly dominant. Consequently, satisfaction of reported preferences should not be taken as evidence of welfare properties of a matching without qualifications. The use of a common entrance examination may be more cost effective than a system based on college-specific entrance examinations, as colleges do not then need to spend resources on organizing the examinations. However, students have then stronger incentives to perform in the common entrance examination, and there is already evidence that more students retake the matriculation examination in Finland. The overall effect on the costs of organizing entrance examinations is an uncertain empirical matter. The importance of preparation courses is likely to decrease, which saves resources and contributes to socioeconomic equity. On the other hand, making students choose on their study paths earlier in life may erode socioeconomic equity. A larger role for the matriculation examination provides stronger incentives for showing effort in high school, which the policy maker may see as beneficial. While a system with a common entrance examination makes it possible for a student to get admitted to a second preference when she is rejected by her first preference, it remains an empirical question to what extent this reduces the propensity to apply again to competitive colleges. The excess demand for certain colleges is a result of student preferences and is not solvable by any mechanism that gives a strong priority to satisfying student preferences

How to Analyse Retrodictive Probabilities in Inference to the Best Explanation

IBE ('Inference to the best explanation' or abduction) is a popular and highly plausible theory of how we should judge the evidence for claims of past events based on present evidence. It has been notably developed and supported recently by Meyer following Lipton. I believe this theory is essentially correct. This paper supports IBE from a probability perspective, and argues that the retrodictive probabilities involved in such inferences should be analysed in terms of predictive probabilities and a priori probability ratios of initial events. The key point is to separate these two features. Disagreements over evidence can be traced to disagreements over either the a priori probability ratios or predictive conditional ratios. In many cases, in real science, judgements of the former are necessarily subjective. The principles of iterated evidence are also discussed. The Sceptic's position is criticised as ignoring iteration of evidence, and characteristically failing to adjust a priori probability ratios in response to empirical evidence

An investigation of ESOL teachers' attitudes towards teaching about taboo English in the second language classroom

Taboo English is an area of inquiry that has been overlooked in the research literature. Little appears to be published on the phenomenon of taboo language and its teaching implications for adult ESL/EFL students learning conversational English. This study aimed to investigate the attitudes and opinions of 80 ESOL teachers from 10 language schools in Auckland, New Zealand, towards the use of Taboo English in society and their attitudes towards teaching about taboo language to adult learners of conversational English. The project used a questionnaire designed to elicit a combination of both qualitative and quantitative data. Results showed that Taboo English was a valuable aspect of ESOL teachers' linguistic repertoire and that both males and females used taboo words in complex and diverse ways to communicate ideas quickly and efficiently. One of the key findings of the study contradicted the typical stereotype that females are more conservative in their taboo use than males. Another major theme that emerged was the linguistic prejudice towards teaching about Taboo English in the second language classroom. The vast majority of ESOL teachers in the study displayed little, if any, enthusiasm for teaching about taboo words to adult learners of conversational English despite acknowledging that taboo words are frequently heard in society today. This study concludes that Taboo language is an undeniable reality of English language use and that ESOL teachers, preparing adult learners to understand everyday language they will be exposed to in the 'real' world, need to address Taboo English to some degree. By not addressing this controversial language, teachers are insufficiently preparing learners to become empowered communicators in English

The Time Flow Manifesto Chapter 5 Time Flow Physics

In this chapter, we see one way that time flow may force us to develop our physical theory if we add it back into physics proper. Now of course this is speculative in this context, and should be thought of as a model. The two following extracts are from introductions a more complete unified theory. They explain the basic mathematical models that are required to illustrate the point that such models may be plausible. The second extract, ‘the parable of the ants’, introduces us to the ideological-philosophical conflict that prevents such a development being considered in the present generation, which we will go on to next

The Time Flow Manifesto CHAPTER 2 TIME SYMMETRY IN PHYSICS

This chapter starts with a simple conventional presentation of time reversal in physics, and then returns to analyse it, rejects the conventional analysis, and establishes correct principles in their place

Principles of physical time directionality and fallacies of the conventional philosophy

These are the first two chapters from a monograph (The Time Flow Manifesto, Holster, 2013-14; unpublished), defending the concepts of time directionality and time flow in physics and naturalistic metaphysics, against long-standing attacks from the ‘conventional philosophy of physical time’. This monograph sets out to disprove twelve specific “fallacies of the conventional philosophy”, stated in the first section below. These are the foundational principles of the conventional philosophy, which developed in the mid-C20th from positivist-inspired studies. The first chapter begins by re-presenting the basic analysis of time reversal symmetry in the context of probabilistic or non-deterministic processes, removing the first critical error in the conventional account. The second chapter argues for a law-like explanation of physical time asymmetry and irreversibility, and shows how the ‘reversibility paradoxes’ are explained

The Time Flow Manifesto Chapter 4 Metaphysical Time Flow

In the philosophy of time, the neo-positivist is focussed above all else on sustaining the view called the static theory of time, as the very foundation of their scientific metaphysics. This is the deeply held metaphysical conviction of almost all ‘modern philosophical-scientific’ writers on time. In fact it is hardly too much to say that the entire official modern 20th Century philosophy of physics rests on the assumption that the static theory of space-time is the only concept of time we can use in physics. The static theory of time prescribes the representational space for physics as being logically based on space-time – to the point physicists are incapable of conceiving a theory without space-time any longer, and mutter superstitiously among themselves if someone suggests such a thing. By extension, this space-time provides the representation of all reality for the modern scientific materialists, since they believe that everything ultimately reduces to physics. This agenda simultaneously requires discrediting the alternative concept of time flow and the associated traditional metaphysical concepts that it supports. This Chapter explains the concept of time flow and contrasts it with the static or block universe theory as a genuine and natural alternative for a physical ontology