49,390 research outputs found
Completeness Results for Parameterized Space Classes
The parameterized complexity of a problem is considered "settled" once it has
been shown to lie in FPT or to be complete for a class in the W-hierarchy or a
similar parameterized hierarchy. Several natural parameterized problems have,
however, resisted such a classification. At least in some cases, the reason is
that upper and lower bounds for their parameterized space complexity have
recently been obtained that rule out completeness results for parameterized
time classes. In this paper, we make progress in this direction by proving that
the associative generability problem and the longest common subsequence problem
are complete for parameterized space classes. These classes are defined in
terms of different forms of bounded nondeterminism and in terms of simultaneous
time--space bounds. As a technical tool we introduce a "union operation" that
translates between problems complete for classical complexity classes and for
W-classes.Comment: IPEC 201
OM Theory and V-duality
We show that the (M5, M2, M2, MW) bound state solution of eleven
dimensional supergravity recently constructed in hep-th/0009147 is related to
the (M5, M2) bound state one by a finite Lorentz boost along a M5-brane
direction perpendicular to the M2-brane. Given the (M5, M2) bound state as a
defining system for OM theory and the above relation between this system and
the (M5, M2, M2', MW) bound state, we test the recently proposed V-duality
conjecture in OM theory. Insisting to have a decoupled OM theory, we find that
the allowed Lorentz boost has to be infinitesimally small, therefore resulting
in a family of OM theories related by Galilean boosts. We argue that such
related OM theories are equivalent to each other. In other words, V-duality
holds for OM theory as well. Upon compactification on either an electric or a
`magnetic' circle (plus T-dualities as well), the V-duality for OM theory gives
the known one for either noncommutative open string theories or noncommutative
Yang-Mills theories. This further implies that V-duality holds in general for
the little m-theory without gravity.Comment: 17 pages, typos corrected and references adde
Thermodynamic Curvature of the BTZ Black Hole
Some thermodynamic properties of the Ba\~nados-Teitelboim-Zanelli (BTZ) black
hole are studied to get the effective dimension of its corresponding
statistical model. For this purpose, we make use of the geometrical approach to
the thermodynamics: Considering the black hole as a thermodynamic system with
two thermodynamic variables (the mass and the angular momemtum ), we
obtain two-dimensional Riemannian thermodynamic geometry described by positive
definite Ruppeiner metric. From the thermodynamic curvature we find that the
extremal limit is the critical point. The effective spatial dimension of the
statistical system corresponding to the near-extremal BTZ black holes is one.
Far from the extremal point, the effective dimension becomes less than one,
which leads to one possible speculation on the underlying structure for the
corresponding statistical model.Comment: 19 pages, LaTeX with revtex macro, 4 figures in eps file
Numerical simulation of solid tumor blood perfusion and drug delivery during the “vascular normalization window” with antiangiogenic therapy
This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Hindawi PublishingTo investigate the influence of vascular normalization on solid tumor blood perfusion and drug delivery, we used the generated blood vessel network for simulations. Considering the hemodynamic parameters changing after antiangiogenic therapies, the results show that the interstitial fluid pressure (IFP) in tumor tissue domain decreases while the pressure gradient increases during the normalization window. The decreased IFP results in more efficient delivery of conventional drugs to the targeted cancer cells. The outcome of therapies will improve if the antiangiogenic therapies and conventional therapies are carefully scheduled
Constrained structure of ancient Chinese poetry facilitates speech content grouping
Ancient Chinese poetry is constituted by structured language that deviates from ordinary language usage [1, 2]; its poetic genres impose unique combinatory constraints on linguistic elements [3]. How does the constrained poetic structure facilitate speech segmentation when common linguistic [4, 5, 6, 7, 8] and statistical cues [5, 9] are unreliable to listeners in poems? We generated artificial Jueju, which arguably has the most constrained structure in ancient Chinese poetry, and presented each poem twice as an isochronous sequence of syllables to native Mandarin speakers while conducting magnetoencephalography (MEG) recording. We found that listeners deployed their prior knowledge of Jueju to build the line structure and to establish the conceptual flow of Jueju. Unprecedentedly, we found a phase precession phenomenon indicating predictive processes of speech segmentation—the neural phase advanced faster after listeners acquired knowledge of incoming speech. The statistical co-occurrence of monosyllabic words in Jueju negatively correlated with speech segmentation, which provides an alternative perspective on how statistical cues facilitate speech segmentation. Our findings suggest that constrained poetic structures serve as a temporal map for listeners to group speech contents and to predict incoming speech signals. Listeners can parse speech streams by using not only grammatical and statistical cues but also their prior knowledge of the form of language
Non-existence of New Quantum Ergosphere Effect of a Vaidya-type Black Hole
Hawking evaporation of Dirac particles and scalar fields in a Vaidya-type
black hole is investigated by the method of generalized tortoise coordinate
transformation. It is shown that Hawking radiation of Dirac particles does not
exist for components but for components in any
Vaidya-type black holes. Both the location and the temperature of the event
horizon change with time. The thermal radiation spectrum of Dirac particles is
the same as that of Klein-Gordon particles. We demonstrates that there is no
new quantum ergosphere effect in the thermal radiation of Dirac particles in
any spherically symmetry black holes.Comment: Latex, 9 pages, no figure, submitted to Mod. Phys. Lett.
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