Collapsing Shells and the Isoperimetric Inequality for Black Holes

Recent results of Trudinger on Isoperimetric Inequalities for non-convex bodies are applied to the gravitational collapse of a lightlike shell of matter to form a black hole. Using some integral identities for co-dimension two surfaces in Minkowski spacetime, the area $A$ of the apparent horizon is shown to be bounded above in terms of the mass $M$ by the $16 \pi G^2 M^2$, which is consistent with the Cosmic Censorship Hypothesis. The results hold in four spacetime dimensions and above.Comment: 16 pages plain TE

lordif: An R Package for Detecting Differential Item Functioning Using Iterative Hybrid Ordinal Logistic Regression/Item Response Theory and Monte Carlo Simulations

Logistic regression provides a flexible framework for detecting various types of differential item functioning (DIF). Previous efforts extended the framework by using item response theory (IRT) based trait scores, and by employing an iterative process using group--specific item parameters to account for DIF in the trait scores, analogous to purification approaches used in other DIF detection frameworks. The current investigation advances the technique by developing a computational platform integrating both statistical and IRT procedures into a single program. Furthermore, a Monte Carlo simulation approach was incorporated to derive empirical criteria for various DIF statistics and effect size measures. For purposes of illustration, the procedure was applied to data from a questionnaire of anxiety symptoms for detecting DIF associated with age from the Patient--Reported Outcomes Measurement Information System.

Birth of Closed Strings and Death of Open Strings during Tachyon Condensation

The tremendous progress achieved through the study of black holes and branes suggests that their time dependent generalizations called Spacelike branes (S-branes) may prove similarly useful. An example of an established approach to S-branes is to include a string boundary interaction and we first summarize evidence for the death of open string degrees of freedom for the homogeneous rolling tachyon on a decaying brane. Then, we review how to extract the flat S-brane worldvolumes describing the homogeneous rolling tachyon and how large deformations correspond to creation of lower dimensional strings and branes. These S-brane worldvolumes are governed by S-brane actions which are on equal footing to D-brane actions, since they are derived by imposing conformality on the string worldsheet, as well as by analyzing fluctuations of time dependent tachyon configurations. As further examples we generalize previous solutions of the S-brane actions so as to describe multiple decaying and nucleating closed fundamental strings. Conceptually S-brane actions are therefore different from D-brane actions and can provide a description of time dependent strings/branes and possibly their interactions.Comment: 15 pages, 7 eps figures; invited review for Modern Physics Letters A, including new solutions for S-brane actions. v2 published version, minor typos correcte

Topology, Entropy and Witten Index of Dilaton Black Holes

We have found that for extreme dilaton black holes an inner boundary must be introduced in addition to the outer boundary to give an integer value to the Euler number. The resulting manifolds have (if one identifies imaginary time) topology $S^1 \times R \times S^2$ and Euler number $\chi = 0$ in contrast to the non-extreme case with $\chi=2$. The entropy of extreme $U(1)$ dilaton black holes is already known to be zero. We include a review of some recent ideas due to Hawking on the Reissner-Nordstr\"om case. By regarding all extreme black holes as having an inner boundary, we conclude that the entropy of {\sl all} extreme black holes, including $[U(1)]^2$ black holes, vanishes. We discuss the relevance of this to the vanishing of quantum corrections and the idea that the functional integral for extreme holes gives a Witten Index. We have studied also the topology of ``moduli space'' of multi black holes. The quantum mechanics on black hole moduli spaces is expected to be supersymmetric despite the fact that they are not HyperK\"ahler since the corresponding geometry has torsion unlike the BPS monopole case. Finally, we describe the possibility of extreme black hole fission for states with an energy gap. The energy released, as a proportion of the initial rest mass, during the decay of an electro-magnetic black hole is 300 times greater than that released by the fission of an ${}^{235} U$ nucleus.Comment: 51 pages, 4 figures, LaTeX. Considerably extended version. New sections include discussion of the Witten index, topology of the moduli space, black hole sigma model, and black hole fission with huge energy releas

Simple generalizations of Anti-de Sitter space-time

We consider new cosmological solutions which generalize the cosmological patch of the Anti-de Sitter (AdS) space-time, allowing for fluids with equations of state such that $w\neq -1$. We use them to derive the associated full manifolds. We find that these solutions can all be embedded in flat five-dimensional space-time with $--+++$ signature, revealing deformed hyperboloids. The topology and causal-structure of these spaces is therefore unchanged, and closed time-like curves are identified, before a covering space is considered. However the structure of Killing vector fields is entirely different and so we may expect a different structure of Killing horizons in these solutions.Comment: 6 Pages, 5 Figures, Corrections and additions made for publication in Journal of Classical and Quantum Gravit

Normal Modes and No Zero Mode Theorem of Scalar Fields in BTZ Black Hole Spacetime

Eigenfunctions for normal modes of scalar fields in BTZ black hole spacetime are studied. Orthonormal relations among them are derived. Quantization for scalar fields is done and particle number, energy and angular momentum are expressed by the creation and annihilation operators. Allowed physical normal mode region is studied on the basis of the no zero mode theorem. Its implication to the statistical mechanics is also studied.Comment: 11 pages,v2 typos correcte

Generalized (m,k)-Zipf law for fractional Brownian motion-like time series with or without effect of an additional linear trend

We have translated fractional Brownian motion (FBM) signals into a text based on two ''letters'', as if the signal fluctuations correspond to a constant stepsize random walk. We have applied the Zipf method to extract the $\zeta '$ exponent relating the word frequency and its rank on a log-log plot. We have studied the variation of the Zipf exponent(s) giving the relationship between the frequency of occurrence of words of length $m<8$ made of such two letters: $\zeta '$ is varying as a power law in terms of $m$. We have also searched how the $\zeta '$ exponent of the Zipf law is influenced by a linear trend and the resulting effect of its slope. We can distinguish finite size effects, and results depending whether the starting FBM is persistent or not, i.e. depending on the FBM Hurst exponent $H$. It seems then numerically proven that the Zipf exponent of a persistent signal is more influenced by the trend than that of an antipersistent signal. It appears that the conjectured law $\zeta ' = |2H-1|$ only holds near $H=0.5$. We have also introduced considerations based on the notion of a {\it time dependent Zipf law} along the signal.Comment: 24 pages, 12 figures; to appear in Int. J. Modern Phys

Framing Effects on Stigma and Help-Seeking

NPS NRP Executive SummaryThis study examines stigma and related factors that reduce help-seeking in the Navy across the N17 program enterprise. The intended outcome will be to measure effectiveness of changes in language related to the DoD's Integrated Primary Prevention Policy (DoDI 6400.09) and to identify language that encourage help-seeking among Sailors. The research will consider effects of message framing alongside broader influences such as organizational culture and structure, individual differences (e.g., gender, rank, personality) and openness to coaching about life skills. This research plan allows for the possibility that effects of language on stigma and help-seeking may vary among persons and communities within the socio-cultural environment of the Navy. Research methods include review of current literature, conduct of focus group meetings, and surveys of Naval community members. The literature review will establish known principles about how to encourage help-seeking and support formulation of discussion questions, message frames, and scenarios for further exploration via focus groups. The focus groups will include members of various communities within the Navy, inviting their assessment of current practices and attitudes, and their consideration of alternative approaches to encourage help-seeking. Following analysis of focus group data, the survey will collect quantitative data about attitudes toward help-seeking, socio-cultural factors in the environment that may affect stigma and help-seeking, and individual differences that might impact personal attitudes. An interim report following the focus group meetings will identify issues that frequently arise, message frames that participants see as positive or negative, and qualitative assessments of alternative ways to discuss help-seeking. The final report will explain results of the surveys and include recommendations to further support help-seeking among Navy personnel.N1 - Manpower, Personnel, Training & EducationThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Framing Effects on Stigma and Help-Seeking

NPS NRP Technical ReportThis study examines stigma and related factors that reduce help-seeking in the Navy across the N17 program enterprise. The intended outcome will be to measure effectiveness of changes in language related to the DoD's Integrated Primary Prevention Policy (DoDI 6400.09) and to identify language that encourage help-seeking among Sailors. The research will consider effects of message framing alongside broader influences such as organizational culture and structure, individual differences (e.g., gender, rank, personality) and openness to coaching about life skills. This research plan allows for the possibility that effects of language on stigma and help-seeking may vary among persons and communities within the socio-cultural environment of the Navy. Research methods include review of current literature, conduct of focus group meetings, and surveys of Naval community members. The literature review will establish known principles about how to encourage help-seeking and support formulation of discussion questions, message frames, and scenarios for further exploration via focus groups. The focus groups will include members of various communities within the Navy, inviting their assessment of current practices and attitudes, and their consideration of alternative approaches to encourage help-seeking. Following analysis of focus group data, the survey will collect quantitative data about attitudes toward help-seeking, socio-cultural factors in the environment that may affect stigma and help-seeking, and individual differences that might impact personal attitudes. An interim report following the focus group meetings will identify issues that frequently arise, message frames that participants see as positive or negative, and qualitative assessments of alternative ways to discuss help-seeking. The final report will explain results of the surveys and include recommendations to further support help-seeking among Navy personnel.N1 - Manpower, Personnel, Training & EducationThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

Framing Effects on Stigma and Help-Seeking

NPS NRP Project PosterThis study examines stigma and related factors that reduce help-seeking in the Navy across the N17 program enterprise. The intended outcome will be to measure effectiveness of changes in language related to the DoD's Integrated Primary Prevention Policy (DoDI 6400.09) and to identify language that encourage help-seeking among Sailors. The research will consider effects of message framing alongside broader influences such as organizational culture and structure, individual differences (e.g., gender, rank, personality) and openness to coaching about life skills. This research plan allows for the possibility that effects of language on stigma and help-seeking may vary among persons and communities within the socio-cultural environment of the Navy. Research methods include review of current literature, conduct of focus group meetings, and surveys of Naval community members. The literature review will establish known principles about how to encourage help-seeking and support formulation of discussion questions, message frames, and scenarios for further exploration via focus groups. The focus groups will include members of various communities within the Navy, inviting their assessment of current practices and attitudes, and their consideration of alternative approaches to encourage help-seeking. Following analysis of focus group data, the survey will collect quantitative data about attitudes toward help-seeking, socio-cultural factors in the environment that may affect stigma and help-seeking, and individual differences that might impact personal attitudes. An interim report following the focus group meetings will identify issues that frequently arise, message frames that participants see as positive or negative, and qualitative assessments of alternative ways to discuss help-seeking. The final report will explain results of the surveys and include recommendations to further support help-seeking among Navy personnel.N1 - Manpower, Personnel, Training & EducationThis research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.