56 research outputs found
A microscopic model of wave-function dephasing and decoherence in the double-slit experiment
The act of measurement on a quantum state is supposed to "collapse" the state
into one of several eigenstates of the operator corresponding to the observable
being measured. This measurement process is sometimes described as outside
standard quantum-mechanical evolution and not calculable from Schr\"odinger's
equation. There are two general approaches to the study of wave-function
collapse: one called the "consistent" or "decoherent" histories approach and
the other, the "environmental decoherence" approach, which studies the effect
of the environment upon the quantum system, to explain wave-function collapse.
In the "environmental decoherence" approach, one usually studies a
Markovian-approximated Master equation to study the time-evolution of reduced
density matrix and obtains the long-term dependence of the off-diagonal
elements of this matrix. We do not make a Markovian assumption and study a
particularly simple and calculable example. We find, the short-time behavior of
a collapsing system, at least the one considered in this paper, is not
exponential, which is a new result (the long-term behavior is, of course, still
exponential). This allows one to connect the Fermi-golden rule
quadratic-in-time behavior of a transition probability to the exponential
long-time behavior of a collapsing wave-function
An observer's perspective of the Unruh and Hawking effects
The Unruh effect is one of the first calculations of what one would see when
transiting between an inertial reference frame with its quantum field vacuum
state and a non-inertial (specifically, uniformly accelerating) reference
frame. The inertial reference frame's vacuum state would not correspond to the
vacuum state of the non-inertial frame and the observer in that frame would see
radiation, with a corresponding Bose distribution and a temperature
proportional to the acceleration (in natural units).
In this paper, I compute the response of this non-inertial observer to a
single frequency mode in the inertial frame and deduce that, indeed, the
cumulative distribution (over the observer's proper time) of frequencies
observed by the accelerating observer would be the Bose distribution with a
temperature proportional to the acceleration. The conclusion is that the Unruh
effect (and the related Hawking effect) is generic, in that it would appear
with any incoming incoherent state and the Bose distribution is obtained as a
consequence of the non-inertial frame's motion, rather than some special
property of the quantum vacuum
Document Clustering with Map Reduce using Hadoop Framework
Big data is a collection of data sets. It is so enormous and complex that it becomes difficult to processes and analyse using normal database management tools or traditional data processing applications. Big data is having many challenges. The main problem of the big data is store and retrieve of the data from the search engines. Document data is also growing rapidly in the eon of internet. Analysing document data is very important for many applications. Document clustering is the one of the important technique to analyse the document data. It has many applications like organizing large document collection, finding similar documents, recommendation system, duplicate content detection, search optimization. This work is motivated by the reorganization of the need for a well efficient retrieve of the data from massive resources of data repository through the search engines. In this work mainly focused on document clustering for collection of documents in efficient manner using with MapReduce.
DOI: 10.17762/ijritcc2321-8169.15018
X-Ray Scattering Measurements of the Transient Structure of a Driven Charge-Density-Wave
We report time-resolved x-ray scattering measurements of the transient
structural response of the sliding {\bf Q} charge-density-wave (CDW) in
NbSe to a reversal of the driving electric field. The observed time scale
characterizing this response at 70K varies from 15 msec for driving
fields near threshold to 2 msec for fields well above threshold. The
position and time-dependent strain of the CDW is analyzed in terms of a
phenomenological equation of motion for the phase of the CDW order parameter.
The value of the damping constant, eV
seconds \AA, is in excellent agreement with the value
determined from transport measurements. As the driving field approaches
threshold from above, the line shape becomes bimodal, suggesting that the CDW
does not depin throughout the entire sample at one well-defined voltage.Comment: revtex 3.0, 7 figure
Implications of a holographic density of states on inflation
There is theoretical evidence that the number of degrees of freedom in quantum fields decreases as one studies them at extremely short distances. This emerges from the study of entropy of black holes, as well as from holographic theories in AdS geometries. Presumably a theory of quantum gravity will provide an explicit description of how the number of degrees of freedom thin out as one studies high energy scales. We do not have a comprehensive theory of how such a thinning of degrees of freedom would occur. It is likely that there might be residual (and measurable) effects at larger length scales, though this might be significant only near the Planck scale. There are very few instances in Nature where one might be able to see effects of this thinning. One promising venue is in the phenomenon of inflation, produced in the simplest models through a scalar inflaton field in a potential with a flat (“slow-roll”) part as well as a potential well. During inflation, fluctuations of small length scales are stretched to large scales and then exit the Hubble horizon. We compute the effect of such a thinning of degrees of freedom upon the running of the spectral index of quantum fluctuations of the inflaton and deduce that this will lead to a small positive power of wave vector (opposite to the usual , i.e., negative power correction). Some comments are then made about the impact on observations (or non-observations) of such fluctuations (Martin J
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