15,828 research outputs found
Time-reversal and parity conservation for gravitating quarks
The complex mass term of a quark does not violate time-reversal or parity in
gravitational interactions, in spite of an axial anomaly.Comment: 4 pages, to appear in Classical and Quantum Gravit
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Set covering and set partitioning: a collection of test problems
It is now well established that set covering and set partitioning models play a central role
in many scheduling applications. There are many algorithms which solve these
problems. In order to test and validate such implementations we have collected a range
of test problems taken from different contexts. A brief description of these models,
their applications and summary model data, are supplied in this paper
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A tree search approach for the solution of set problems using alternative relaxations
A number of alternative relaxations for the family of set problems (FSP) in general and set covering problems (SCP) in particular are introduced and discussed. These are (i) Network flow relaxation, (ii) Assignment relaxation, (iii) Shortest route relaxation, (iv) Minimum spanning tree relaxation. A unified tree search method is developed which makes use of these relaxations. Computational experience of processing a collection of test problems is reported
Quantum Information Paradox: Real or Fictitious?
One of the outstanding puzzles of theoretical physics is whether quantum
information indeed gets lost in the case of Black Hole (BH) evaporation or
accretion. Let us recall that Quantum Mechanics (QM) demands an upper limit on
the acceleration of a test particle. On the other hand, it is pointed out here
that, if a Schwarzschild BH would exist, the acceleration of the test particle
would blow up at the event horizon in violation of QM. Thus the concept of an
exact BH is in contradiction of QM and quantum gravity (QG). It is also
reminded that the mass of a BH actually appears as an INTEGRATION CONSTANT of
Einstein equations. And it has been shown that the value of this integration
constant is actually zero. Thus even classically, there cannot be finite mass
BHs though zero mass BH is allowed. It has been further shown that during
continued gravitational collapse, radiation emanating from the contracting
object gets trapped within it by the runaway gravitational field. As a
consequence, the contracting body attains a quasi-static state where outward
trapped radiation pressure gets balanced by inward gravitational pull and the
ideal classical BH state is never formed in a finite proper time. In other
words, continued gravitational collapse results in an "Eternally Collapsing
Object" which is a ball of hot plasma and which is asymptotically approaching
the true BH state with M=0 after radiating away its entire mass energy. And if
we include QM, this contraction must halt at a radius suggested by highest QM
acceleration. In any case no EH is ever formed and in reality, there is no
quantum information paradox.Comment: 8 pages in Pramana Style, 6 in Revtex styl
Three-point Green function of massless QED in position space to lowest order
The transverse part of the three-point Green function of massless QED is
determined to the lowest order in position space. Taken together with the
evaluation of the longitudinal part in arXiv:0803.2630, this gives a relation
for QED which is analogous to the star-triangle relation. We relate our result
to conformal-invariant three-point functions.Comment: 8 page
Complex fermion mass term, regularization and CP violation
It is well known that the CP violating theta term of QCD can be converted to
a phase in the quark mass term. However, a theory with a complex mass term for
quarks can be regularized so as not to violate CP, for example through a zeta
function. The contradiction is resolved through the recognition of a dependence
on the regularization or measure. The appropriate choice of regularization is
discussed and implications for the strong CP problem are pointed out.Comment: REVTeX, 4 page
Ranking Investment Projects
This paper describes conditions under which one investment project dominates a second project in terms of net present value, irrespective of the choice of the discount rate. The resulting partial ordering of projects has certain similarities to stochastic dominance. However, the structure of the net present value function leads to characterizations that are quite specific to this context. Our theorems use Bernstein's (1915) innovative results on the representation and approximation of polynomials, as well as other general results from the theory of equations, to characterize the partial ordering. We also show how the ranking is altered when the range of discount rates is limited or the rate varies period by period.
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