343 research outputs found

    Origin of 1015−101610^{15}-10^{16}G Magnetic Fields in the Central Engine of Gamma Ray Bursts

    Full text link
    Various authors have suggested that the gamma-ray burst (GRB) central engine is a rapidly rotating, strongly magnetized, (∼1015−1016(\sim 10^{15}-10^{16} G) compact object. The strong magnetic field can accelerate and collimate the relativistic flow and the rotation of the compact object can be the energy source of the GRB. The major problem in this scenario is the difficulty of finding an astrophysical mechanism for obtaining such intense fields. Whereas, in principle, a neutron star could maintain such strong fields, it is difficult to justify a scenario for their creation. If the compact object is a black hole, the problem is more difficult since, according to general relativity it has "no hair" (i.e., no magnetic field). Schuster, Blackett, Pauli, and others have suggested that a rotating neutral body can create a magnetic field by non-minimal gravitational-electromagnetic coupling (NMGEC). The Schuster-Blackett form of NMGEC was obtained from the Mikhail and Wanas's tetrad theory of gravitation (MW). We call the general theory NMGEC-MW. We investigate here the possible origin of the intense magnetic fields ∼1015−1016\sim 10^{15}-10^{16} G in GRBs by NMGEC-MW. Whereas these fields are difficult to explain astrophysically, we find that they are easily explained by NMGEC-MW. It not only explains the origin of the ∼1015−1016\sim 10^{15}-10^{16}G fields when the compact object is a neutron star, but also when it is a black hole.Comment: 9 pages, accepted for publication in JCA

    Evolving Lorentzian Wormholes

    Full text link
    Evolving Lorentzian wormholes with the required matter satisfying the Energy conditions are discussed. Several different scale factors are used and the corresponding consequences derived. The effect of extra, decaying (in time) compact dimensions present in the wormhole metric is also explored and certain interesting conclusions are derived for the cases of exponential and Kaluza--Klein inflation.Comment: 10 pages( RevTex, Twocolumn format), Two figures available on request from the first author. transmission errors corrected

    Fate of the first traversible wormhole: black-hole collapse or inflationary expansion

    Full text link
    We study numerically the stability of Morris & Thorne's first traversible wormhole, shown previously by Ellis to be a solution for a massless ghost Klein-Gordon field. Our code uses a dual-null formulation for spherically symmetric space-time integration, and the numerical range covers both universes connected by the wormhole. We observe that the wormhole is unstable against Gaussian pulses in either exotic or normal massless Klein-Gordon fields. The wormhole throat suffers a bifurcation of horizons and either explodes to form an inflationary universe or collapses to a black hole, if the total input energy is respectively negative or positive. As the perturbations become small in total energy, there is evidence for critical solutions with a certain black-hole mass or Hubble constant. The collapse time is related to the initial energy with an apparently universal critical exponent. For normal matter, such as a traveller traversing the wormhole, collapse to a black hole always results. However, carefully balanced additional ghost radiation can maintain the wormhole for a limited time. The black-hole formation from a traversible wormhole confirms the recently proposed duality between them. The inflationary case provides a mechanism for inflating, to macroscopic size, a Planck-sized wormhole formed in space-time foam.Comment: 10 pages, RevTeX4, 11 figures, epsf.st

    Static and dynamic traversable wormhole geometries satisfying the Ford-Roman constraints

    Full text link
    It was shown by Ford and Roman in 1996 that quantum field theory severely constrains wormhole geometries on a macroscopic scale. The first part of this paper discusses a wide class of wormhole solutions that meet these constraints. The type of shape function used is essentially generic. The constraints are then discussed in conjunction with various redshift functions. Violations of the weak energy condition and traversability criteria are also considered. The second part of the paper analyzes analogous time-dependent (dynamic) wormholes with the aid of differential forms. It is shown that a violation of the weak energy condition is not likely to be avoidable even temporarily.Comment: 16 pages AMSTe

    (n+1)(n+1)-Dimensional Lorentzian Wormholes in an Expanding Cosmological Background

    Full text link
    We discuss (n+1)(n+1)-dimensional dynamical wormholes in an evolving cosmological background with a throat expanding with time. These solutions are examined in the general relativity framework. A linear relation between diagonal elements of an anisotropic energy-momentum tensor is used to obtain the solutions. The energy-momentum tensor elements approach the vacuum case when we are far from the central object for one class of solutions. Finally, we discuss the energy-momentum tensor which supports this geometry, taking into account the energy conditions .Comment: 12 pages, 14 figures, references added, to appear in Astophysics and Space Scienc

    Gravitational radiation from gamma-ray bursts as observational opportunities for LIGO and VIRGO

    Full text link
    Gamma-ray bursts are believed to originate in core-collapse of massive stars. This produces an active nucleus containing a rapidly rotating Kerr black hole surrounded by a uniformly magnetized torus represented by two counter-oriented current rings. We quantify black hole spin-interactions with the torus and charged particles along open magnetic flux-tubes subtended by the event horizon. A major output of Egw=4e53 erg is radiated in gravitational waves of frequency fgw=500 Hz by a quadrupole mass-moment in the torus. Consistent with GRB-SNe, we find (i) Ts=90s (tens of s, Kouveliotou et al. 1993), (ii) aspherical SNe of kinetic energy Esn=2e51 erg (2e51 erg in SN1998bw, Hoeflich et al. 1999) and (iii) GRB-energies Egamma=2e50 erg (3e50erg in Frail et al. 2001). GRB-SNe occur perhaps about once a year within D=100Mpc. Correlating LIGO/Virgo detectors enables searches for nearby events and their spectral closure density 6e-9 around 250Hz in the stochastic background radiation in gravitational waves. At current sensitivity, LIGO-Hanford may place an upper bound around 150MSolar in GRB030329. Detection of Egw thus provides a method for identifying Kerr black holes by calorimetry.Comment: to appear in PRD, 49

    An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics

    Get PDF
    For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types

    Patient-reported treatment toxicity and adverse events in Black and White women receiving chemotherapy for early breast cancer

    Get PDF
    Purpose: It is not known whether chemotherapy-related symptom experiences differ between Black and White women with early breast cancer (Stage I–III) receiving current chemotherapy regimens and, in turn, influences dose delay, dose reduction, early treatment discontinuation, or hospitalization. Methods: Patients self-reported their race and provided symptom reports for 17 major side effects throughout chemotherapy. Toxicity and adverse events were analyzed separately for anthracycline and non-anthracycline regimens. Fisher’s exact tests and two-sample t-tests compared baseline patient characteristics. Modified Poisson regression estimated relative risks of moderate, severe, or very severe (MSVS) symptom severity, and chemotherapy-related adverse events.Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary.no changes Results: In 294 patients accrued between 2014 and 2020, mean age was 58 (SD13) and 23% were Black. For anthracycline-based regimens, the only significant difference in MSVS symptoms was in lymphedema (41% Black vs 20% White, p =.04) after controlling for axillary surgery. For non-anthracycline regimens, the only significant difference was MSVS peripheral neuropathy (41% Blacks vs. 23% White) after controlling for taxane type (p =.05) and diabetes (p =.05). For all other symptoms, severity scores were similar. Dose reduction differed significantly for non-anthracycline regimens (49% Black vs. 25% White, p =.01), but not for anthracycline regimens or in dose delay, early treatment discontinuation, or hospitalization for either regimen. Conclusion: Except for lymphedema and peripheral neuropathy, Black and White patients reported similar symptom severity during adjuvant chemotherapy. Dose reductions in Black patients were more common for non-anthracycline regimens. In this sample, there were minimal differences in patient-reported symptoms and other adverse outcomes in Black versus White patients
    • …
    corecore