Finally, results from Gravity Probe-B

Nearly fifty years after its inception, the Gravity Probe B satellite mission delivers the first measurements of how a spinning gyroscope precesses in the gravitational warping of spacetime.Comment: A Viewpoint article, published in Physics 4, 43 (2011), available at http://physics.aps.org/articles/v4/43 Submitted to the arXiv by permission of the American Physical Societ

Dynamic temperature selection for parallel-tempering in Markov chain Monte Carlo simulations

Modern problems in astronomical Bayesian inference require efficient methods for sampling from complex, high-dimensional, often multi-modal probability distributions. Most popular methods, such as Markov chain Monte Carlo sampling, perform poorly on strongly multi-modal probability distributions, rarely jumping between modes or settling on just one mode without finding others. Parallel tempering addresses this problem by sampling simultaneously with separate Markov chains from tempered versions of the target distribution with reduced contrast levels. Gaps between modes can be traversed at higher temperatures, while individual modes can be efficiently explored at lower temperatures. In this paper, we investigate how one might choose the ladder of temperatures to achieve more efficient sampling, as measured by the autocorrelation time of the sampler. In particular, we present a simple, easily-implemented algorithm for dynamically adapting the temperature configuration of a sampler while sampling. This algorithm dynamically adjusts the temperature spacing to achieve a uniform rate of exchanges between chains at neighbouring temperatures. We compare the algorithm to conventional geometric temperature configurations on a number of test distributions and on an astrophysical inference problem, reporting efficiency gains by a factor of 1.2-2.5 over a well-chosen geometric temperature configuration and by a factor of 1.5-5 over a poorly chosen configuration. On all of these problems a sampler using the dynamical adaptations to achieve uniform acceptance ratios between neighbouring chains outperforms one that does not.Comment: 21 pages, 21 figure

Scaled-free objects II

This work creates two categories of "array-weighted sets" for the purposes of constructing universal matrix-normed spaces and algebras. These universal objects have the analogous universal property to the free vector space, lifting maps completely bounded on a generation set to a completely bounded linear map of the matrix-normed space. Moreover, the universal matrix-normed algebra is used to prove the existence of a free product for matrix-normed algebras using algebraic methods.Comment: 46 pages. Version 4 fixed a few minor typos. Version 3 added matricial completion; fixed an arithmetic error in Example 3.5.10. Version 2 added a preliminaries section on weighted sets and matricial Banach spaces, incorporating much of "Matricial Banach spaces" in summary; fixed a domain issue in Lemma 3.3.2; simplified Examples 3.5.10 and 4.11; added more proofs to Sections 4 and

The PhD in construction management

The PhD process is uncertain, idiosyncratic and vague. Research into the management of PhDs has proved very useful for supervisors and students. It is important for everyone involved in the process to be aware of what can be done to improve the likelihood of success for PhD studies. There are many ways of tackling a PhD and it is not possible to describe construction management as a generic type of study. Rather, construction management is a source of problems and data, whereas solutions and approaches need to be based within established academic disciplines. The clear definition of a research project is an essential prerequisite for success. Although PhDs are difficult, there are many things that can be done by departments, supervisors and students to ease the difficulties. In the long run, the development of an active and dynamic research community is dependent upon a steady flow of high quality PhDs. No-one benefits from an uncompleted or failed PhD

Disrupt, Deny, Dismantle: A Special Operations Forces (SOF) Model for Combatting New Terrorism

Terrorism in the new millennium has morphed drastically since the 1970s. The terrorist organizations of today are a hybrid between the insurgent group models of the 1960s and modern terrorist organizations such as Al Qaeda. This hybrid model has created what has become a transnational insurgency recruited, trained, and led by major terrorist networks such as the Islamic State of Iraq and the Levant (ISIL). Even smaller regional groups such as Boko Haram have surpassed merely conducting terrorist attacks. These smaller groups are also focused on controlling territory. Tan (2008) refers to this change as “New Terrorism”. To combat New Terrorism, a combination of counterinsurgency tactics and counterterrorism tactics must be employed. This study will examine the need to define roles and responsibilities for various organization and various echelons through the introduction of a new Special Operations Forces model; Disrupt, Deny, Dismantle. The acronym to be used for this model is D3. This model recommends different tactics, techniques, and procedures for forces not specifically assigned the counterterrorism mission. As new terrorism continues to change, only counterterrorism forces should be tasked with the Find Fix Finish, Exploit, Analyze, and Disseminate (F3EAD) model of targeting (Counterterrorism 2014). All other military and law enforcement elements should disrupt and deny the enemy in support of the counterterrorism effort. This study is based on extensive research and the author’s 23 years of experience serving in U.S. Army Special Forces. Throughout his career, the author interacted with people from various social, economic, and professional backgrounds throughout the Middle East, Africa, and the Balkans

Two Generator groups acting on the complex hyperbolic plane

This is an expository article about groups generated by two isometries of the complex hyperbolic plane.Comment: 49 pages, 10 figures. It will appear as a chapter of Volume VI of the Handbook of Teichmuller theor