Bending of light in the framework of R + R2 gravity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Deflexão de fótons pelo sol no contexto da teoria de gravitação R+R2

Pós-graduação em Física - IFT

Prediction of R plus R-2 gravity for the deflection of a photon passing close to the Sun

The cross-section for the scattering of a photon by the Sun's gravitational field, treated as an external field, is computed in the framework of R + R-2 gravity. Using this result, we found that for a photon just grazing the Sun's surface the deflection is 1.75 which is exactly the same as that given by Einstein's theory. An explanation for this pseudo-paradox is provided.

Quadratic gravity theories in 2+1 dimensions and the topological Chern-Simons term

The addition of a topological Chern-Simons term to three-dimensional higher-derivative gravity is not a good therapy to cure the nonunitarity of the aforementioned theory. Moreover, R+R-2 gravity in (2+1)D, which is unitary at the tree level, becomes tree-level nonunitary when it is augmented by the abovementioned topological term. Therefore, unlike what is claimed in the literature, topological higher-derivative gravity in (2+1)D is not tree-level unitary and neither is topological three-dimensional R+R-2 gravity.

Unavoidable conflict between massive gravity models and massive topological terms

Massive gravity models in (2 + 1) dimensions, such as those obtained by adding to Einstein's gravity the usual Fierz-Pauli, or the more complicated Ricci scalar squared (R-2), terms, are tree level unitary. Interesting enough these seemingly harmless systems have their unitarity spoiled when they are augmented by a Chern-Simons term. Furthermore, if the massive topological term is added to R + R-munu(2) gravity, or to R + R-munu(2), + R-2 gravity (higher-derivative gravity), which are nonunitary at the tree level, the resulting models remain nonunitary. Therefore, unlike the common belief, as well as the claims in the literature, the coexistence between three-dimensional massive gravity models and massive topological terms is conflicting.

广西银屏富硼花岗岩岩浆-热液演化地球化学研究

已有的研究表明，与富B花岗岩有关的岩浆-热液体系以富含电气石矿物为特征，B和其它挥发分一起参与了岩浆分异、流体演化、围岩蚀变以及金属迁移和沉积的一系列过程。但至今B与Sn-W矿床之间是否存在协同性仍是个不解之迷。 电气石是B的主要寄主矿物，并且电气石被认为是成岩成矿的良好指示剂。目前，国内外对富B岩浆体系性状以及B对成岩成矿的作用研究相对比较缺乏。广西银屏细粒花岗岩是花山复式岩体最晚期的侵入岩相，不仅花岗岩中结晶有大量的电气石，而且在发育的晶洞中含有大量的电气石矿物。本文通过对银屏细粒花岗岩和晶洞中电气石化学组成、石英中流体包裹体的系统研究，探讨富B花岗岩形成和岩浆-热液体系演化地球化学特征，并对B与Sn矿化是否存在耦合关系的潜在性进行评价。 通过对富B花岗岩的研究，我们得到以下几点重要结论： (1) 银屏细粒花岗岩以高硅、高钾、富碱、低磷、准铝质为特征，具有较高的FeO*/MgO，富集大离子亲石元素、高场强元素和稀土元素。银屏细粒花岗岩的全岩样品显示强烈的稀土“四重效应”及等价不相容元素对 (Nb-Ta、Zr-Hf、Sr-Eu)分异，表明花山花岗岩分异演化晚期阶段存在熔体-流体作用； (2) 细粒花岗岩和晶洞中电气石为富Fe的黑电气石，前者是岩浆成因的，后者是蒸汽相成因的。两种成因电气石化学组成非常一致，几乎不含有过剩Al，Fe/(Fe+Mg)比值集中分布于0.96～0.98之间。Al3+=Fe3+和R++R2+=R3++□是电气石中2个主要置换反应； (3) 花山A型花岗岩形成演化过程中不存在狭义的岩浆-热液过渡阶段，形成细粒花岗岩的岩浆具有极高的粘度，大量的饱和蒸汽相被高粘度的熔体捕获﹑圈闭，气泡生长是岩浆去气的主要方式；尽管岩浆在相对高的氧逸度条件下分异演化，但由于缺乏岩浆-热液演化过程，在银屏岩体范围内不太可能发生有规模的锡石-石英脉型矿化作用； (4) 晶洞石英显示仅含有气液包裹体，而无其他类型包裹体共存，表明岩浆流体演化晚期为均匀的单一相。晚期流体的温压范围在150～265 °C，41～72 MPa之间。

Search for diphoton events with large missing transverse energy in 7 TeV proton-proton collisions with the ATLAS detector

A search for diphoton events with large missing transverse energy is presented. The data were collected with the ATLAS detector in proton-proton collisions at √s=7 TeV at the CERN Large Hadron Collider and correspond to an integrated luminosity of 3.1 pb⁻¹. No excess of such events is observed above the standard model background prediction. In the context of a specific model with one universal extra dimension with compactification radius R and gravity-induced decays, values of 1/R<729 GeV are excluded at 95% C. L., providing the most sensitive limit on this model to date.

Validation of a paradigm to measure instrumental aggression (iap) on a sample of male adolescents with adjustment problems

Aggressive behavior can be classified in hostile and instrumental aggressions (anderson & bushman, 2002). this classification is mostly synonymously used with reactive and proactive aggression, whereas the differences between hostile and instrumental aggression lie on three dimensions, the primary goal, amount of anger and planning and calculation(bushman & anderson, 2001). although there are rating instruments and experimental paradigms to measure hostile aggression, there is no instrument to measure instrumental aggression. the following study will present an account to measure instrumental aggression with an experimental laboratory paradigm. the instrument was firstly tested on two samples of normal young adolescents (n1 = 100; amage. = 19.14; n2 = 60; amage. = 21.46). the first study revealed a strong correlation with a laboratory aggression paradigm measuring hostile aggression, but no correlations with self-reported aggression in the buss and perry questionnaire. these results were replicated in a second study, revealing an additional correlation with aggressive but not adaptive assertiveness. secondly the instrument was part of the evaluation of the reasoning and rehabilitation program r&r2 (ross, hilborn & lidell, 1984) in an institution for male adolescents with adjustment problems in switzerland. the r&r2 is a cognitive behavioral group therapy to reduce antisocial and promote prosocial cognitions and behavior. the treatment group (n= 16; rangeage = 15-17) is compared to a no treatment control group (n=24; rangeage = 17-19) preand post- treatment. further aggressive behavior was surveyed and experimentally measured. hostile rumination, aggressive and adaptive assertiveness, emotional and social competence were included in the measurement to estimate construct validity.

Wirksamkeit des Programms "Reasoning and Rehabilitation Revised" für inhaftierte Frauen in der Schweiz - eine Erkundungsstudie

Hintergrund Bei dem revidierten Programm „Reasoning and Rehabilitation“ (R&R2) handelt es sich um einen gruppentherapeutischen Ansatz zur Behandlung spezifischer Probleme von Straftätern. Hier werden erstmals Effekte der deutschsprachigen Version für Mädchen und junge Frauen berichtet. Material und Methode Die Effekte des Gruppentrainings wurden bei 11 inhaftierten Frauen durch standardisierte Fragebogen erfasst. Hierbei interessierten Veränderungen sozial-interpersoneller, motivationaler, psychopathologischer und emotionsregulatorischer Merkmale. Zudem wurden die Zufriedenheit mit der Behandlung und der klinische Eindruck erhoben. Ergebnisse Die erfassten proximalen Effektmaße unterstützen überwiegend die Hypothese einer Wirksamkeit des R&R2 bei Frauen. Das Programm erwies sich als veränderungsinduzierend und wurde gut angenommen. Schlussfolgerung Die Ergebnisse dieser isolierten Evaluation des R&R2-Trainings bei Frauen weisen auf positive Veränderungen spezieller Problembereiche hin. Jedoch werden weiterführende Studien zum intra- und extramuralen Verhalten sowie distalen Rückfälligkeitsmaß benötigt.

Visible near infra-red (VisNIR) spectroscopy for predicting soil organic carbon in Ethiopia

Over the past few decades, the advantages of the visible-near infra-red (VisNIR) diffuse reflectance spectrometer (DRS) method have enabled prediction of soil organic carbon (SOC). In this study, SOC was predicted using regression models for samples taken from three sites (Gununo, Maybar and Anjeni) in Ethiopia. SOC was characterized in laboratory using conventional wet chemistry and VisNIR-DRS methods. Principal component analysis (PCA), principal component regression (PCR) and partial least square regression (PLS) models were developed using Unscrambler X 10.2. PCA results show that the first two components accounted for a minimum of 96% variation which increased for individual sites and with data treatments. Correlation (r), coefficient of determination (R2) and residual prediction deviation (RPD) were used to rate four models built. PLS model (r, R2, RPD) values for Anjeni were 0.9, 0.9 and 3.6; for Gununo values 0.6, 0.3 and 1.2; for Maybar values 0.6, 0.3 and 0.9, and for the three sites values 0.7, 0.6 and 1.5, respectively. PCR model values (r, R2, RPD) for Anjeni were 0.9, 0.8 and 2.7; for Gununo values 0.5, 0.3 and 1; for Maybar values 0.5, 0.1 and 0.7, and for the three sites values 0.7, 0.5 and 1.2, respectively. Comparison and testing of models shows superior performance of PLS to PCR. Models were rated as very poor (Maybar), poor (Gununo and three sites) and excellent (Anjeni). A robust model, Anjeni, is recommended for prediction of SOC in Ethiopia.

On gravitational fields of stars in f(R) gravity theories

Einstein's general relativity is a classical theory of gravitation: it is a postulate on the coupling between the four-dimensional, continuos spacetime and the matter fields in the universe, and it yields their dynamical evolution. It is believed that general relativity must be replaced by a quantum theory of gravity at least at extremely high energies of the early universe and at regions of strong curvature of spacetime, cf. black holes. Various attempts to quantize gravity, including conceptually new models such as string theory, have suggested that modification to general relativity might show up even at lower energy scales. On the other hand, also the late time acceleration of the expansion of the universe, known as the dark energy problem, might originate from new gravitational physics. Thus, although there has been no direct experimental evidence contradicting general relativity so far - on the contrary, it has passed a variety of observational tests - it is a question worth asking, why should the effective theory of gravity be of the exact form of general relativity? If general relativity is modified, how do the predictions of the theory change? Furthermore, how far can we go with the changes before we are face with contradictions with the experiments? Along with the changes, could there be new phenomena, which we could measure to find hints of the form of the quantum theory of gravity? This thesis is on a class of modified gravity theories called f(R) models, and in particular on the effects of changing the theory of gravity on stellar solutions. It is discussed how experimental constraints from the measurements in the Solar System restrict the form of f(R) theories. Moreover, it is shown that models, which do not differ from general relativity at the weak field scale of the Solar System, can produce very different predictions for dense stars like neutron stars. Due to the nature of f(R) models, the role of independent connection of the spacetime is emphasized throughout the thesis.

The R-x, R2-x Planes; Some New Ideas for the Study of Nonlinear Systems

Use of some new planes such as the R-x, R2-x (where R represents in the n-dimensional phase space, the radius vector from the origin to any point on the trajectory described by the system) is suggested for analysis of nonlinear systems of any kind. The stability conditions in these planes are given. For easy understanding of the method, the transformation from the phase plane to the R-x, R2-x planes is brought out for second-order systems. In general, while these planes serve as useful as the phase plane, they have proved to be simpler in determining quickly the general behavior of certain classes of second-order nonlinear systems. A chart and a simple formula are suggested to evaluate time easily from the R-x and R2-x trajectories, respectively. A means of solving higher-order nonlinear systems is also illustrated. Finally, a comparative study of the trajectories near singular points on the phase plane and on the new planes is made.

On the long standing issue of an R phi(2) coupling between gravity and a massless free scalar field

Using 2-body trees on a flat space background, it is shown that the actions A[g, φ] = (Latin small letter esh) d4x√-g [(R/2K) + (1/2)(gμν ∂μφ∂νφ + λRφ2)] and Ā[ḡ, φ̄] = (Latin small letter esh) d4x√ - ḡ [(R̄/2k) + (1/2) ḡμν∂μφ̄∂ νφ] describe the same theory at the tree-level in this case. We also demonstrate the quantum equivalence (at one-loop) of the barred and unbarred systems for λ == -1/6 (conformal coupling).