ترغب بنشر مسار تعليمي؟ اضغط هنا

How many atoms get excited when they decay?

89   0   0.0 ( 0 )
 نشر من قبل Philip Daniel Blocher
 تاريخ النشر 2017
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

We analyze the time evolution of a two-level system prepared in a superposition of its ground state and radiatively unstable excited state. We show that by choosing appropriate means of detection of the radiated field, we can steer the evolution of the emitter and herald its preparation in the fully excited state. We determine the probability for the occurrence of this excitation during the decay of a remote emitter.



قيم البحث

اقرأ أيضاً

It is shown that, contrary to an existing claim, the near equality between the lifetime of the sun and the timescale of biological evolution on earth does not necessarily imply that extraterrestrial civilizations are exceedingly rare. Furthermore, on the basis of simple assumptions it is demonstrated that a near equality between these two timescales may be the most probable relation. A calculation of the cosmic history of carbon production which is based on the recently determined history of the star formation rate suggests that the most likely time for intelligent civilizations to emerge in the universe, was when the universe was already older then about 10 billion years (for an assumed current age of about 13 billion years).
In our model, $n$ traders interact with each other and with a central bank; they are taxed on the money they make, some of which is dissipated away by corruption. A generic feature of our model is that the richest trader always wins by consuming all the others: another is the existence of a threshold wealth, below which all traders go bankrupt. The two-trader case is examined in detail,in the socialist and capitalist limits, which generalise easily to $n>2$. In its mean-field incarnation, our model exhibits a two-time-scale glassy dynamics, as well as an astonishing universality.When preference is given to local interactions in finite neighbourhoods,a novel feature emerges: instead of at most one overall winner in the system,finite numbers of winners emerge, each one the overlord of a particular region.The patterns formed by such winners (metastable states) are very much a consequence of initial conditions, so that the fate of the marketplace is ruled by its past history; hysteresis is thus also manifested.
129 - Gary A Mamon 2010
We apply a simple, one-equation, galaxy formation model on top of the halos and subhalos of a high-resolution dark matter cosmological simulation to study how dwarf galaxies acquire their mass and, for better mass resolution, on over 10^5 halo merger trees, to predict when they form their stars. With the first approach, we show that the large majority of galaxies within group- and cluster-mass halos have acquired the bulk of their stellar mass through gas accretion and not via galaxy mergers. We deduce that most dwarf ellipticals are not built up by galaxy mergers. With the second approach, we constrain the star formation histories of dwarfs by requiring that star formation must occur within halos of a minimum circular velocity set by the evolution of the temperature of the IGM, starting before the epoch of reionization. We qualitatively reproduce the downsizing trend of greater ages at greater masses and predict an upsizing trend of greater ages as one proceeds to masses lower than m_crit. We find that the fraction of galaxies with very young stellar populations (more than half the mass formed within the last 1.5 Gyr) is a function of present-day mass in stars and cold gas, which peaks at 0.5% at m_crit=10^6-8 M_Sun, corresponding to blue compact dwarfs such as I Zw 18. We predict that the baryonic mass function of galaxies should not show a maximum at masses above 10^5.5, M_Sun, and we speculate on the nature of the lowest mass galaxies.
187 - Chi-Fang Chen , Kohtaro Kato , 2020
We study whether one can write a Matrix Product Density Operator (MPDO) as the Gibbs state of a quasi-local parent Hamiltonian. We conjecture this is the case for generic MPDO and give supporting evidences. To investigate the locality of the parent H amiltonian, we take the approach of checking whether the quantum conditional mutual information decays exponentially. The MPDO we consider are constructed from a chain of 1-input/2-output (`Y-shaped) completely-positive maps, i.e. the MPDO have a local purification. We derive an upper bound on the conditional mutual information for bistochastic channels and strictly positive channels, and show that it decays exponentially if the correctable algebra of the channel is trivial. We also introduce a conjecture on a quantum data processing inequality that implies the exponential decay of the conditional mutual information for every Y-shaped channel with trivial correctable algebra. We additionally investigate a close but nonequivalent cousin: MPDO measured in a local basis. We provide sufficient conditions for the exponential decay of the conditional mutual information of the measured states, and numerically confirmed they are generically true for certain random MPDO.
Using the deepest data yet obtained, we find no evidence preferring compaction-triggered quenching---where rapid increases in galaxy density truncate star formation---over a null hypothesis in which galaxies age at constant surface density ($Sigma_ee quiv M_*/2pi r_{e}^{2}$). Results from two fully empirical analyses and one quenching-free model calculation support this claim at all $zleq3$: (1) Qualitatively, galaxies mean $U-V$ colors at $6.5lesssimlogSigma_e/{rm M_odot},{rm kpc}^{-2}lesssim10$ have reddened at rates/times correlated with $Sigma_e$, implying that there is no density threshold at which galaxies turn red but that $Sigma_e$ sets the pace of maturation; (2) Quantitatively, the abundance of $log M_*/{rm M_odot}geq9.4$ red galaxies never exceeds that of the total population a quenching time earlier at any $Sigma_e$, implying that galaxies need not transit from low to high densities before quenching; (3) Applying $dlog r_{e}/dt =1/2,dlog M_*/dt$ to a suite of lognormal star formation histories reproduces the evolution of the size--mass relation at $log M_*geq10$. All results are consistent with evolutionary rates being set ab initio by global densities, with denser objects evolving faster than less-dense ones towards a terminal quiescence induced by gas depletion or other $sim$Hubble-timescale phenomena. Unless stellar ages demand otherwise, observed $Sigma_e$ thresholds need not bear any physical relation to quenching beyond this intrinsic density--formation epoch correlation, adding to Lilly & Carollos arguments to that effect.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا