Can a pseudo-symmetry solve the cosmological constant problem?

A general no-go theorem dampens hope that the cosmological constant problem can be solved by a local symmetry mechanism. The possibility is considered here that this no-go theorem can be avoided by a pseudo-symmetry. A simple macroscopic effective field theory is constructed which admits an enhanced pseudo-symmetry in the absence of a cosmological term. It is pointed out that this pseudo-symmetry is an exact classical invariance of superstrings. The conjecture that this pseudo-symmetry survives in the quantum theory has several interesting consequences.Comment: Changes in language (including new title), and assorted perestroika. One new consequence of conjecture. 10 pages, uuencoded Postscript file. To appear in Phys.Lett.

On the Inequivalence of Renormalization and Self-Adjoint Extensions for Quantum Singular Interactions

A unified S-matrix framework of quantum singular interactions is presented for the comparison of self-adjoint extensions and physical renormalization. For the long-range conformal interaction the two methods are not equivalent, with renormalization acting as selector of a preferred extension and regulator of the unbounded Hamiltonian.Comment: 19 pages, including 2 figures. The title and abstract were changed to more accurately reflect the content. The text was rearranged into sections, with several equations and multiple paragraphs added for clarity; and a few typos were corrected. The central equations and concepts remain unchanged

Anomalous Commutator Algebra for Conformal Quantum Mechanics

The structure of the commutator algebra for conformal quantum mechanics is considered. Specifically, it is shown that the emergence of a dimensional scale by renormalization implies the existence of an anomaly or quantum-mechanical symmetry breaking, which is explicitly displayed at the level of the generators of the SO(2,1) conformal group. Correspondingly, the associated breakdown of the conservation of the dilation and special conformal charges is derived.Comment: 23 pages. A few typos corrected in the final version (which agrees with the published Phys. Rev. D article

Renormalized Path Integral for the Two-Dimensional Delta-Function Interaction

A path-integral approach for delta-function potentials is presented. Particular attention is paid to the two-dimensional case, which illustrates the realization of a quantum anomaly for a scale invariant problem in quantum mechanics. Our treatment is based on an infinite summation of perturbation theory that captures the nonperturbative nature of the delta-function bound state. The well-known singular character of the two-dimensional delta-function potential is dealt with by considering the renormalized path integral resulting from a variety of schemes: dimensional, momentum-cutoff, and real-space regularization. Moreover, compatibility of the bound-state and scattering sectors is shown.Comment: 26 pages. The paper was significantly expanded and numerous equations were added for the sake of clarity; the main results and conclusions are unchange

SO(2,1) conformal anomaly: Beyond contact interactions

The existence of anomalous symmetry-breaking solutions of the SO(2,1) commutator algebra is explicitly extended beyond the case of scale-invariant contact interactions. In particular, the failure of the conservation laws of the dilation and special conformal charges is displayed for the two-dimensional inverse square potential. As a consequence, this anomaly appears to be a generic feature of conformal quantum mechanics and not merely an artifact of contact interactions. Moreover, a renormalization procedure traces the emergence of this conformal anomaly to the ultraviolet sector of the theory, within which lies the apparent singularity.Comment: 11 pages. A few typos corrected in the final versio

Os olhares de futuros professores sobre a metodologia de trabalho de projeto

Tendo feito a formação de futuros professores do 1º ciclo do ensino básico na metodologia de trabalho de projeto, foi nossa intenção recolher as opiniões deles sobre a utilização dessa metodologia na educação escolar. Os resultados obtidos mostram que os futuros professores compreenderam o conceito e a prática da metodologia de trabalho de projeto, com opiniões próximas daqueles descritos teoricamente, referindo várias vantagens na sua utilização no processo de ensino e de aprendizagem. Por esta razão, são, também, da opinião que é importante a formação de professores nessa metodologia de ensino e de aprendizagem

Control of time-delayed Markovian jump linear systems

Motivated by networked control systems, a class of Markovian jump linear switching systems with time-delays that are random is considered. Unlike assumptions made in traditional control theory, network control systems no longer assumes that information or signals exchanged between subsystems (or components) are ideal or perfect. Indeed, imperfect information exchanges such as unexpected delays and partial or total loss of information make the network control systems unique and difficult to deal with. Fortunately, it is known that a Markovian jump linear system is an appropriate mathematical representation of the systems with sudden changes of dynamical behavior. For this reason, the mathematical framework considered in this thesis is Markovian jump linear systems with time-delays. Conditions for stability of the Makovian jump linear systems with time-delays that are fixed and known apriorly are first developed. The condition is extended to a stabilizability condition that enables the formulation of a control design algorithm. The controller designed is a state feedback which depends on the switching mode of the Markovian jump linear system to be controlled, and guarantees stochastic stability of the overall system. The results are further extended to deal with the case when the plant to be controlled is uncertain. Given the assumption that the plant\u27s uncertainty is described in terms of a bounded norm, a control design technique is developed to compute a state feedback controller that ensures the stochastic stability of the overall system under the prescribed plant perturbations. The case when the time-delay is random, time-varying, and unknown is considered next. Stability and stabilizability conditions for such systems have been derived and subsequently the control design algorithm has been obtained. An algorithm to compute a robust controller for the uncertain system is also developed. The results obtained are all depending on the switching mode of the Markovian jump linear switching systems, but independent from the delay. Better and sharper results are expected from the conditions depending on delay. Motivated by this, stability, stabilizability, and robust stabilizability conditions that are functions of time-delay presented in the system are developed. Each condition developed is in the form of Linear Matrix Inequalities that can be efficiently solved by standard computational tools such as Matlab. Each condition is also illustrated by an example. A systems engineering approach is employed and used to implement and verify the subsystems design for Markovian Jump Linear Systems with time-varying delays for a network control system

Persistence of African American Females in Engineering: The Mathematics Identity Factor

To continue as global science and technological leaders, the United States is motivated to create a diverse, engineering workforce. One way of diversifying the engineering workforce is to address the disparity of women engineers. Although concerted efforts to improve retention rates of women in engineering are ongoing, women have earned only 5.6% of all undergraduate engineering degrees, with only 1% attributed to African American women (NSF, 2015b). African American women are commonly included in racial or gender-focused studies on persistence; however, few studies assess the effect of multiple identities to persistence. This exploratory study examined the relationship of persistence, measured by intent to persist, to multiple identities (social, professional, and racial) of African American female engineering students. Forward regression analyses were conducted and results indicated that the participant’s mathematical identities were more salient to them than their racial or gender identities. Also, the values these women placed on being an engineer and belonging to the group were principal aspects of their professional identity. Additionally, negative affect and stereotype threat were found significant predictors of intent to persist. Keywords: women engineers, persistence, identity, African American engineer

Interrogating the precancerous evolution of pathway dysfunction in lung squamous cell carcinoma using XTABLE

Lung squamous cell carcinoma (LUSC) is a type of lung cancer with a dismal prognosis that lacks adequate therapies and actionable targets. This disease is characterized by a sequence of low- and high-grade preinvasive stages with increasing probability of malignant progression. Increasing our knowledge about the biology of these premalignant lesions (PMLs) is necessary to design new methods of early detection and prevention, and to identify the molecular processes that are key for malignant progression. To facilitate this research, we have designed XTABLE (Exploring Transcriptomes of Bronchial Lesions), an open-source application that integrates the most extensive transcriptomic databases of PMLs published so far. With this tool, users can stratify samples using multiple parameters and interrogate PML biology in multiple manners, such as two- and multiple-group comparisons, interrogation of genes of interests, and transcriptional signatures. Using XTABLE, we have carried out a comparative study of the potential role of chromosomal instability scores as biomarkers of PML progression and mapped the onset of the most relevant LUSC pathways to the sequence of LUSC developmental stages. XTABLE will critically facilitate new research for the identification of early detection biomarkers and acquire a better understanding of the LUSC precancerous stages.</p