24,857 research outputs found
The Coronal Temperatures of Low-Mass Main-Sequence Stars
Aims. We study the X-ray emission of low-mass main-sequence stars to derive a
reliable general scaling law between coronal temperature and the level of X-ray
activity.
Methods. We collect ROSAT measurements of hardness ratios and X-ray
luminosities for a large sample of stars to derive which stellar X-ray emission
parameter is most closely correlated with coronal temperature. We calculate
average coronal temperatures for a sample of 24 low-mass main-sequence stars
with measured emission measure distributions (EMDs) collected from the
literature. These EMDs are based on high-resolution X-ray spectra measured by
XMM-Newton and Chandra.
Results. We confirm that there is one universal scaling relation between
coronal average temperature and surface X-ray flux, Fx, that applies to all
low-mass main-sequence stars. We find that coronal temperature is related to Fx
by Tcor=0.11 Fx^0.26, where Tcor is in MK and Fx is in erg/s/cm^2.Comment: 5 pages, 3 figures, 1 table; accepted for publication in A&
Strong Interaction Effects in Stop Pair Production at Colliders
We discuss perturbative and non-perturbative strong interaction effects in
the pair production of stop squarks () at colliders.
Events with an additional hard gluon allow to detect or exclude stop pair
production even in scenarios with very small mass splitting between
and an invisible lightest supersymmetric particle (LSP). Such
events can also help to establish that transforms as a triplet
under . We also carefully study non-perturbative
fragmentation, which is currently not well understood: not only is the
fragmentation function not known very well, but also there are
ambiguities in the algorithm employed to model fragmentation. We present
numerical results both for CERN LEP-183 and for a proposed future
collider operating at center-of-mass energy GeV.Comment: 16 pages and 4 figure
Synthesis and characterization of a novel Y-Fe phase via kinetic neutron diffraction
Kinetic in situ neutron diffraction has been used to study the crystallization of
amorphous Y67Fe33. The results show that partial crystallization first occurs
close to 300 â—¦C where the Y phase is formed. The entire sample crystallizes
at 390 â—¦C and new Bragg peaks appear, signifying the formation of a novel
Y–Fe phase. This new phase coexists with Y to 450 ◦C when the Bragg peaks
associated with this phase rapidly decrease in intensity and YFe2 also coexisting
with Y, emerges as the final crystallization product. Rietveld refinement
shows that the new phase crystallizes into a hexagonal structure, space group
P63/mmc, with a = 12.8893(7) Å, c = 11.7006(9) Å and γ = 120◦
Introduction to Nietzsche on Mind and Nature
This chapter provides summaries of the chapter of this book and introduces the major themes and debates addressed in the volume. Discussed are Nietzsche’s metaphysics; his philosophy of mind in light of contemporary views; the question of panpsychism of Beyond Good and Evil 36; the rejection of dualism in favour of monism, in particular a monism of value; Nietzsche’s positions on consciousness and embodied cognition in light of recent cognitive science; a conception of freedom and agency based on an intrinsically motivating; embodied sense of self-efficacy; a Nietzschean account of valuing understood as drive-induced affective orientations of which an agent approves; the idea of ressentiment conceived as a process of intentional, not reflectively strategic, self-deception about one’s own conscious mental states; and a defence of a Nietzschean naturalism
A Quantum Quasi-Harmonic Nonlinear Oscillator with an Isotonic Term
The properties of a nonlinear oscillator with an additional term ,
characterizing the isotonic oscillator, are studied. The nonlinearity affects
to both the kinetic term and the potential and combines two nonlinearities
associated to two parameters, and , in such a way that for
all the characteristics of of the standard isotonic system are
recovered. The first part is devoted to the classical system and the second
part to the quantum system. This is a problem of quantization of a system with
position-dependent mass of the form , with a
-dependent non-polynomial rational potential and with an additional
isotonic term. The Schr\"odinger equation is exactly solved and the
-dependent wave functions and bound state energies are explicitly
obtained for both .Comment: two figure
A possible chiral spin-liquid phase in non-centrosymmetric BaCoO
Based on a symmetry approach, we propose a possible explanation of the weak
ferromagnetic component recently observed in YBaCoFeO (Valldor et al.
Phys Rev B, 224426 (2011)) and other isostructural compounds in the
high-temperature spin-liquid phase. Due to the polar nature of their crystal
structure, a coupling between time-odd scalar spin chirality which we suggest
as the primary order parameter and macroscopic magnetization is possible as
follows from the general form of the appropriate free-energy invariant. The
deduced pseudoproper coupling between both physical quantities provides a
unique possibility to study the critical behaviour of the chiral order
parameter
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