2,367 research outputs found
Hybrid Memristor-CMOS (MeMOS) based Logic Gates and Adder Circuits
Practical memristor came into picture just few years back and instantly
became the topic of interest for researchers and scientists. Memristor is the
fourth basic two-terminal passive circuit element apart from well known
resistor, capacitor and inductor. Recently, memristor based architectures has
been proposed by many researchers. In this paper, we have designed a hybrid
Memristor-CMOS (MeMOS) logic based adder circuit that can be used in numerous
logic computational architectures. We have also analyzed the transient response
of logic gates designed using MeMOS logic circuits. MeMOS use CMOS 180 nm
process with memristor to compute boolean logic operations. Various parameters
including speed, ares, delay and power dissipation are computed and compared
with standard CMOS 180 nm logic design. The proposed logic shows better area
utilization and excellent results from existing CMOS logic circuits at standard
1.8 V operating voltage.Comment: 10 pages, 13 figures, 5 tables, journa
Proposal for a new quantum theory of gravity
We recall a classical theory of torsion gravity with an asymmetric metric,
sourced by a Nambu-Goto + Kalb-Ramond string . We explain why this is a
significant gravitational theory, and in what sense classical general
relativity is an approximation to it. We propose that a non-commutative
generalisation of this theory (in the sense of Connes' non-commutative geometry
and Adler's Trace Dynamics) is a `quantum theory of gravity'. The theory is in
fact a classical matrix dynamics with only two fundamental constants -- the
square of the Planck length and the speed of light, along with the two string
tensions as parameters. The guiding symmetry principle is that the theory
should be covariant under general coordinate transformations of non-commuting
coordinates.The action for this non-commutative torsion gravity can be
elegantly expressed as an invariant area integral, and represents an atom of
space-time-matter. The statistical thermodynamics of a large number of such
atoms yields the laws of quantum gravity and quantum field theory, at
thermodynamic equilibrium. Spontaneous localisation caused by large
fluctuations away from equilibrium is responsible for the emergence of
classical space-time and the field equations of classical general relativity.
The resolution of the quantum measurement problem by spontaneous collapse is an
inevitable consequence of this process. Quantum theory and general relativity,
are both seen as emergent phenomena, resulting from coarse-graining of the
underlying non-commutative geometry. We explain the profound role played by
entanglement in this theory: entanglement describes interaction between the
atoms of space-time-matter, and indeed entanglement appears to be more
fundamental than quantum theory or space-time. We also comment on possible
implications for black hole entropy and evaporation, and for cosmology.Comment: v2: 32 pages, 1 figure, Section I borrows some text (overview of
trace dynamics) from arXiv:1701.09132v1 [quant-ph], revised in response to
reviewer comments: list of revisions appended after bibliography; accepted
for publication in Zeitschrift fur Naturforschun
Space-time from collapse of the wave-function
We propose that space-time results from collapse of the wave function of
macroscopic objects, in quantum dynamics. We first argue that there ought to
exist a formulation of quantum theory which does not refer to classical time.
We then propose such a formulation by invoking an operator Minkowski space-time
on the Hilbert space. We suggest relativistic spontaneous localisation as the
mechanism for recovering classical space-time from the underlying theory.
Quantum interference in time could be one possible signature for operator time,
and in fact may have been already observed in the laboratory, on attosecond
time scales. A possible prediction of our work seems to be that interference in
time will not be seen for `time slit' separations significantly larger than 100
attosecond, if the ideas of operator time and relativistic spontaneous
localisation are correct.Comment: v2: 12 pages, 6 figures, clarifying remarks added, has text overlap
with arXiv:1806.01297 [gr-qc], to appear in Zeitschrift f\"ur Naturforschung
Nature does not play dice at the Planck scale
We start from classical general relativity coupled to matter fields. Each
configuration variable and its conjugate momentum, as also space-time points,
are raised to the status of matrices [equivalently operators]. These matrices
obey a deterministic Lagrangian dynamics at the Planck scale. By
coarse-graining this matrix dynamics over time intervals much larger than
Planck time, one derives quantum theory as a low energy emergent approximation.
If a sufficiently large number of degrees of freedom get entangled, spontaneous
localisation takes place, leading to the emergence of classical space-time
geometry and a classical universe. In our theory, dark energy is shown to be a
large-scale quantum gravitational phenomenon. Quantum indeterminism is not
fundamental, but results from our not probing physics at the Planck scale.Comment: v2: 8 pages; Typo corrected, Honourable mention, GRF essay contest
2020. Accepted for publication in Int. J. Mod. Phys.
General relativity, torsion, and quantum theory
We recall some of the obstacles which arise when one tries to reconcile the
general theory of relativity with quantum theory. We consider the possibility
that gravitation theories which include torsion, and not only curvature,
provide better insight into a quantum theory of gravity. We speculate on how
the Dirac equation and Einstein gravity could be thought of as limiting cases
of a gravitation theory which possesses torsion.Comment: 14 pages; published in Current Science [Special Section: 100 Years of
General Relativity
Possible role of gravity in collapse of the wave-function: a brief survey of some ideas
This article is a brief survey of some approaches to implementing the
suggestion that collapse of the wave function is mediated by gravity. These
approaches include: a possible connection between the problem of time and
problem of quantum measurement, decoherence models based on space-time
uncertainty, the Schr\"{o}dinger-Newton equation, attempts to introduce gravity
into collapse models such as CSL, ideas based on the black hole - elementary
particle complementarity, and the possible role of a complex space-time metric.Comment: 16 pages, one figure, submitted to J. Phys. Conf. Series [proceedings
of the conference DICE2014: Spacetime - Matter - Quantum Mechanics,
Castiglioncello (Tuscany) September 15-19, 2014 Eds. H-T. Elze et al.
Quantum theory and the structure of space-time
We argue that space and space-time emerge as a consequence of dynamical
collapse of the wave function of macroscopic objects. Locality and separability
are properties of our approximate, emergent universe. At the fundamental level,
space-time is non-commutative, and dynamics is non-local and non-separable.Comment: v2: 12 pages, edited version of an essay written for the FQXi essay
contest (2016), minor typos in v1 corrected, to appear in Zeitschrift fur
Naturforschung
A new length scale for quantum gravity
We show why and how Compton wavelength and Schwarzschild radius should be
combined into one single new length scale, which we call the
Compton-Schwarzschild length. Doing so offers a resolution of the black hole
information loss paradox, and suggests Planck mass remnant black holes as
candidates for dark matter. It also compels us to introduce torsion, and
identify the Dirac field with a complex torsion field. Dirac equation, and
Einstein equations, are shown to be mutually dual limiting cases of an
underlying gravitation theory which involves the Compton-Schwarzschild length
scale, and includes a complex torsion field.Comment: 7 pages, 1 figure; v2 - minor typo corrected, Honorable Mention in
the Gravity Research Foundation 2017 Awards for Essays on Gravitatio
The problem of time and the problem of quantum measurement
Quantum theory depends on an external classical time, and there ought to
exist an equivalent reformulation of the theory which does not depend on such a
time. The demand for the existence of such a reformulation suggests that
quantum theory is an approximation to a stochastic non-linear theory. The
stochastic non-linearity provides a dynamical explanation for the collapse of
the wave-function during a quantum measurement. Hence the problem of time and
the measurement problem are related to each other: the search for a solution
for the former problem naturally implies a solution for the latter problem.Comment: 14 pages, 4 figures, based on a talk given at Quantum Malta 2012,
submitted to the volume The Forgotten Present (running title) Thomas Filk and
Albrecht von Muller [Eds.
A new length scale, and modified Einstein-Cartan-Dirac equations for a point mass
We have recently proposed a new action principle for combining Einstein
equations and the Dirac equation for a point mass. We used a length scale
, dubbed the Compton-Schwarzschild length, to which the Compton
wavelength and Schwarzschild radius are small mass and large mass
approximations, respectively. Here we write down the field equations which
follow from this action. We argue that the large mass limit yields Einstein
equations, provided we assume wave function collapse and localisation for large
masses. The small mass limit yields the Dirac equation. We explain why the
Kerr-Newman black hole has the same gyromagnetic ratio as the Dirac electron,
both being twice the classical value. The small mass limit also provides
compelling reasons for introducing torsion, which is sourced by the spin
density of the Dirac field. There is thus a symmetry between torsion and
gravity: torsion couples to quantum objects through Planck's constant
(but not ) and is important in the microscopic limit. Whereas gravity
couples to classical matter, as usual, through Newton's gravitational constant
(but not ), and is important in the macroscopic limit. We construct
the Einstein-Cartan-Dirac equations which include the length . We find
a potentially significant change in the coupling constant of the torsion driven
cubic non-linear self-interaction term in the Dirac-Hehl-Datta equation. We
speculate on the possibility that gravity is not a fundamental interaction, but
emerges as a consequence of wave function collapse, and that the gravitational
constant maybe expressible in terms of Planck's constant and the parameters of
dynamical collapse models.Comment: 12 pages; this article is a follow-up of arXiv:1704.00747v2 [gr-qc];
remarks on `cubic Dirac fermions in Dirac semi-metals' added on page 7;
paragraph added on page 8 to quantitatively compare spin density and mass
density; references added; v3: clarifying remarks added after Eqn. (13),
conclusions unchanged, references updated, published in Int. J. Mod. Phy
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