4,201 research outputs found
A three-qubit interpretation of BPS and non-BPS STU black holes
Following the recent trend we develop further the black hole analogy between
quantum information theory and the theory of extremal stringy black hole
solutions. We show that the three-qubit interpretation of supersymmetric black
hole solutions in the STU model can be extended also to include
non-supersymmetric ones. First we show that the black hole potential can be
expressed as one half the norm of a suitably chosen three-qubit entangled state
containing the quantized charges and the moduli. The extremization of the black
hole potential in terms of this entangled state amounts to either supressing
bit flip errors (BPS-case) or allowing very special types of flips transforming
the states between different classes of non-BPS solutions. We are illustrating
our results for the example of the D2-D6 system. In this case the bit flip
errors are corresponding to sign flip errors of the charges originating from
the number of D2 branes. After moduli stabilization the states depending
entirely on the charges are maximally entangled graph states (of the triangle
graph) well-known from quantum information theory. An N=8 interpretation of the
STU-model in terms of a mixed state with fermionic purifications is also given.Comment: 35 page
Evolutionary trees: an integer multicommodity max-flow-min-cut theorem
In biomathematics, the extensions of a leaf-colouration of a binary tree to the whole vertex set with minimum number of colour-changing edges are extensively studied. Our paper generalizes the problem for trees; algorithms and a Menger-type theorem are presented. The LP dual of the problem is a multicommodity flow problem, for which a max-flow-min-cut theorem holds. The problem that we solve is an instance of the NP-hard multiway cut problem
Role of hexagonal boron nitride in protecting ferromagnetic nanostructures from oxidation
Ferromagnetic contacts are widely used to inject spin polarized currents into
non-magnetic materials such as semiconductors or 2-dimensional materials like
graphene. In these systems, oxidation of the ferromagnetic materials poses an
intrinsic limitation on device performance. Here we investigate the role of
ex-situ transferred chemical vapour deposited hexagonal boron nitride (hBN) as
an oxidation barrier for nanostructured cobalt and permalloy electrodes. The
chemical state of the ferromagnets was investigated using X-ray photoemission
electron microscopy owing to its high sensitivity and lateral resolution. We
have compared the oxide thickness formed on ferromagnetic nanostructures
covered by hBN to uncovered reference structures. Our results show that hBN
reduces the oxidation rate of ferromagnetic nanostructures suggesting that it
could be used as an ultra-thin protection layer in future spintronic devices.Comment: 7 pages, 6 figure
Equation of state at finite baryon density based on lattice QCD
We employ the lattice QCD data on Taylor expansion coefficients to extend our
previous parametrization of the equation of state to finite baryon density.
When we take into account lattice spacing and quark mass dependence of the
hadron masses, the Taylor coefficients at low temperature are equal to those of
hadron resonance gas. Thus the equation of state is smoothly connected to the
hadron resonance gas equation of state at low temperatures. We also show how
the elliptic flow is affected by this equation of state at the maximum SPS
energy.Comment: 4 pages, 4 figures, Paraller talk at Quark Matter 2011, 22-28 May
2011, Annecy, Franc
On Fluctuations of Conserved Charges : Lattice Results Versus Hadron Resonance Gas
We compare recent lattice results on fluctuations and correlations of
strangeness, baryon number and electric charge obtained with p4 improved
staggered action with the prediction of hadron resonance gas model. We show
that hadron resonance gas can describe these fluctuations reasonably well if
the hadron properties are as calculated on the lattice.Comment: 4 pages, LaTeX, uses jpconf.cls, to appear in the proceedings of 26th
Winter Workshop on Nuclear Dynamic
Explaining the elongated shape of 'Oumuamua by the Eikonal abrasion model
The photometry of the minor body with extrasolar origin (1I/2017 U1)
'Oumuamua revealed an unprecedented shape: Meech et al. (2017) reported a shape
elongation b/a close to 1/10, which calls for theoretical explanation. Here we
show that the abrasion of a primordial asteroid by a huge number of tiny
particles ultimately leads to such elongated shape. The model (called the
Eikonal equation) predicting this outcome was already suggested in Domokos et
al. (2009) to play an important role in the evolution of asteroid shapes.Comment: Accepted by the Research Notes of the AA
Strange and charm quark-pair production in strong non-Abelian field
We have investigated strange and charm quark-pair production in the early
stage of heavy ion collisions. Our kinetic model is based on a Wigner function
method for fermion-pair production in strong non-Abelian fields. To describe
the overlap of two colliding heavy ions we have applied the time-dependent
color field with a pulse-like shape. The calculations have been performed in an
SU(2)-color model with finite current quark masses. For strange quark-pair
production the obtained results are close to the Schwinger limit, as we
expected. For charm quark the large inverse temporal width of the field pulse,
instead of the large charm quark mass, determines the efficiency of the
quark-pair production. Thus we do not observe the expected suppression of charm
quark-pair production connecting to the usual Schwinger-formalism, but our
calculation results in a relatively large charm quark yield. This effect
appears in Abelian models as well, demonstrating that particle-pair production
for fast varying non-Abelian gluon field strongly deviates from the Schwinger
limit for charm quark. We display our results on number densities for light,
strange, charm quark-pairs, and different suppression factors as the function
of characteristic time of acting chromo-electric field.Comment: 6 pages, 2 figures; to appear in the proceedings of the International
Conference on Strangeness in Quark matter (SQM2008), Beijing, China, Oct
6-10, 2008; version accepted to J. Phys.
An Observational Evidence for the Difference Between the Short and Long Gamma-Ray Bursts
The intrinsic fluence and duration distributions of gamma-ray bursts are well represented by log-normal
distributions. This allows a bivariate log-normal distribution fit to be made to the BATSE short and long bursts
separately. A statistically significant difference between the long and short groups is found. We argue that the
effect is probably real. Applying the CramĂ©râs theorem these results lead to some predictions for models of long
and short bursts
Detecting Wage Under-reporting Using a Double Hurdle Model
We estimate a double hurdle (DH) model of the Hungarian wage distribution assuming censoring at the minimum wage and wage under-reporting (i.e. compensation consisting of the minimum wage, subject to taxation, and an unreported cash supplement). We estimate the probability of under-reporting for minimum wage earners, simulate their genuine earnings and classify them and their employers as 'cheaters' and 'non-cheaters'. In the possession of the classification we check how cheaters and non-cheaters reacted to the introduction of a minimum social security contribution base, equal to 200 per cent of the minimum wage, in 2007. The findings suggest that cheaters were more likely to raise the wages of their minimum wage earners to 200 per cent of the minimum wage thereby reducing the risk of tax audit. Cheating firms also experienced faster average wage growth and slower output growth. The results suggest that the DH model is able to identify the loci of wage under-reporting with some precision.tax evasion, double hurdle model, Hungary
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