7,291 research outputs found
Exploring Vacuum Structure around Identity-Based Solutions
We explore the vacuum structure in bosonic open string field theory expanded
around an identity-based solution parameterized by . Analyzing the
expanded theory using level truncation approximation up to level 20, we find
that the theory has the tachyon vacuum solution for . We also find
that, at , there exists an unstable vacuum solution in the expanded
theory and the solution is expected to be the perturbative open string vacuum.
These results reasonably support the expectation that the identity-based
solution is a trivial pure gauge configuration for , but it can be
regarded as the tachyon vacuum solution at .Comment: 12 pages, 5 figures; new numerical data up to level (20,60) included;
Contribution to the proceedings of "Second International Conference on String
Field Theory and Related Aspects" (Steklov Mathematical Institute, Moscow,
Russia, April 12-19, 2009
Open String Field Theory around Universal Solutions
We study the physical spectrum of cubic open string field theory around
universal solutions, which are constructed using the matter Virasoro operators
and the ghost and anti-ghost fields. We find the cohomology of the new BRS
charge around the solutions, which appear with a ghost number that differs from
that of the original theory. Considering the gauge-unfixed string field theory,
we conclude that open string excitations perturbatively disappear after the
condensation of the string field to the solutions.Comment: 14 pages, LaTeX with ptptex.cls, typos correcte
Regularization of identity based solution in string field theory
We demonstrate that an Erler-Schnabl type solution in cubic string field
theory can be naturally interpreted as a gauge invariant regularization of an
identity based solution. We consider a solution which interpolates between an
identity based solution and ordinary Erler-Schnabl one. Two gauge invariant
quantities, the classical action and the closed string tadpole, are evaluated
for finite value of the gauge parameter. It is explicitly checked that both of
them are independent of the gauge parameter.Comment: 9 pages, minor typos corrected and references adde
Computationally efficient algorithms for the two-dimensional Kolmogorov-Smirnov test
Goodness-of-fit statistics measure the compatibility of random samples against some theoretical or reference probability distribution function. The classical one-dimensional Kolmogorov-Smirnov test is a non-parametric statistic for comparing two empirical distributions which defines the largest absolute difference between the two cumulative distribution functions as a measure of disagreement. Adapting this test to more than one dimension is a challenge because there are 2^d-1 independent ways of ordering a cumulative distribution function in d dimensions. We discuss Peacock's version of the Kolmogorov-Smirnov test for two-dimensional data sets which computes the differences between cumulative distribution functions in 4n^2 quadrants. We also examine Fasano and Franceschini's variation of Peacock's test, Cooke's algorithm for Peacock's test, and ROOT's version of the two-dimensional Kolmogorov-Smirnov test. We establish a lower-bound limit on the work for computing Peacock's test of
Omega(n^2.lg(n)), introducing optimal algorithms for both this and Fasano and Franceschini's test, and show that Cooke's algorithm is not a faithful implementation of Peacock's test. We also discuss and evaluate parallel algorithms for Peacock's test
Quantum Coherence of Relic Neutrinos
We argue that in at least a portion of the history of the universe the relic
background neutrinos are spatially-extended, coherent superpositions of mass
states. We show that an appropriate quantum mechanical treatment affects the
neutrino mass values derived from cosmological data. The coherence scale of
these neutrino flavor wavepackets can be an appreciable fraction of the causal
horizon size, raising the possibility of spacetime curvature-induced
decoherence.Comment: 4 pages, 4 figures; matches publication in PR
The Location of the Nucleus of NGC 1068 and the Three-dimensional Structure of Its Nuclear Region
The HST archival UV imaging polarimetry data of NGC 1068 is re-examined.
Through an extensive estimation of the observational errors, we discuss whether
the distribution of the position angles (PAs) of polarization is simply
centrosymmetric or not. Taking into account the effect of a bad focus at the
time of the observation, we conclude that, within the accuracy of HST/FOC
polarimetry, the PA distribution is completely centrosymmetric. This means that
the UV polarization originates only from scattering of the radiation from a
central point-like source.
However, our analysis shows that the most probable location of the nucleus is
only ~0.''08 (~6pc) south from the brightest cloud called ``cloud B''. The
error circle of 99% confidence level extends to cloud B and to ``cloud A''
which is about 0.''2 south of cloud B. By this FOC observation, Cloud B is only
marginally rejected as the nucleus.
Assuming that the UV flux is dominated by electron-scattered light, we have
also derived a three-dimensional structure of the nuclear region. The inferred
distribution suggests a linear structure which could be related to the radio
jet.Comment: 19 pages, 14 figures, to be published in the Astrophysical Journa
Neutrino Burst-Generated Gravitational Radiation From Collapsing Supermassive Stars
We estimate the gravitational radiation signature of the electron/positron
annihilation-driven neutrino burst accompanying the asymmetric collapse of an
initially hydrostatic, radiation-dominated supermassive object suffering the
Feynman-Chandrasekhar instability. An object with a mass
, with primordial metallicity, is
an optimal case with respect to the fraction of its rest mass emitted in
neutrinos as it collapses to a black hole: lower initial mass objects will be
subject to scattering-induced neutrino trapping and consequently lower
efficiency in this mode of gravitational radiation generation; while higher
masses will not get hot enough to radiate significant neutrino energy before
producing a black hole. The optimal case collapse will radiate several percent
of the star's rest mass in neutrinos and, with an assumed small asymmetry in
temperature at peak neutrino production, produces a characteristic linear
memory gravitational wave burst signature. The timescale for this signature,
depending on redshift, is to , optimal for proposed
gravitational wave observatories like DECIGO. Using the response of that
detector, and requiring a signal-to-noise ratio SNR 5, we estimate that
collapse of a supermassive star could produce a
neutrino burst-generated gravitational radiation signature detectable to
redshift . With the envisioned ultimate DECIGO design sensitivity,
we estimate that the linear memory signal from these events could be detectable
with SNR to .Comment: 15 pages, 8 figure
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