44 research outputs found
Coherent Control for a Two-level System Coupled to Phonons
The interband polarizations induced by two phase-locked pulses in a
semiconductor show strong interference effects depending on the time tau_1
separating the pulses. The four-wave mixing signal diffracted from a third
pulse delayed by tau is coherently controlled by tuning tau_1. The four-wave
mixing response is evaluated exactly for a two-level system coupled to a single
LO phonon. In the weak coupling regime it shows oscillations with the phonon
frequency which turn into sharp peaks at multiples of the phonon period for a
larger coupling strength. Destructive interferences between the two
phase-locked pulses produce a splitting of the phonon peaks into a doublet. For
fixed tau but varying tau_1 the signal shows rapid oscillations at the
interband-transition frequency, whose amplitude exhibits bursts at multiples of
the phonon period.Comment: 4 pages, 4 figures, RevTex, content change
Extended quantum conditional entropy and quantum uncertainty inequalities
Quantum states can be subjected to classical measurements, whose
incompatibility, or uncertainty, can be quantified by a comparison of certain
entropies. There is a long history of such entropy inequalities between
position and momentum. Recently these inequalities have been generalized to the
tensor product of several Hilbert spaces and we show here how their derivations
can be shortened to a few lines and how they can be generalized. All the
recently derived uncertainty relations utilize the strong subadditivity (SSA)
theorem; our contribution relies on directly utilizing the proof technique of
the original derivation of SSA.Comment: 4 page
Extrapolating SMBH correlations down the mass scale: the case for IMBHs in globular clusters
Empirical evidence for both stellar mass black holes M_bh<10^2 M_sun) and
supermassive black holes (SMBHs, M_bh>10^5 M_sun) is well established.
Moreover, every galaxy with a bulge appears to host a SMBH, whose mass is
correlated with the bulge mass, and even more strongly with the central stellar
velocity dispersion sigma_c, the `M-sigma' relation. On the other hand,
evidence for "intermediate-mass" black holes (IMBHs, with masses in the range
1^2 - 10^5 M_sun) is relatively sparse, with only a few mass measurements
reported in globular clusters (GCs), dwarf galaxies and low-mass AGNs. We
explore the question of whether globular clusters extend the M-sigma
relationship for galaxies to lower black hole masses and find that available
data for globular clusters are consistent with the extrapolation of this
relationship. We use this extrapolated M-sigma relationship to predict the
putative black hole masses of those globular clusters where existence of
central IMBH was proposed. We discuss how globular clusters can be used as a
constraint on theories making specific predictions for the low-mass end of the
M-sigma relation.Comment: 14 pages, 3 figures, accepted for publication in Astrophysics and
Space Science; fixed typos and a quote in Sec.
Desenvolvimento de plĂąntulas de pessegueiro 'Okinawa' inoculadas com micorrizas arbusculares isoladas de pomares de pessegueiros e de vinhedos
Galaxy bulges and their massive black holes: a review
With references to both key and oft-forgotten pioneering works, this article
starts by presenting a review into how we came to believe in the existence of
massive black holes at the centres of galaxies. It then presents the historical
development of the near-linear (black hole)-(host spheroid) mass relation,
before explaining why this has recently been dramatically revised. Past
disagreement over the slope of the (black hole)-(velocity dispersion) relation
is also explained, and the discovery of sub-structure within the (black
hole)-(velocity dispersion) diagram is discussed. As the search for the
fundamental connection between massive black holes and their host galaxies
continues, the competing array of additional black hole mass scaling relations
for samples of predominantly inactive galaxies are presented.Comment: Invited (15 Feb. 2014) review article (submitted 16 Nov. 2014). 590
references, 9 figures, 25 pages in emulateApJ format. To appear in "Galactic
Bulges", E. Laurikainen, R.F. Peletier, and D.A. Gadotti (eds.), Springer
Publishin