2,267 research outputs found
The Relativity of Existence
Despite the success of modern physics in formulating mathematical theories
that can predict the outcome of experiments, we have made remarkably little
progress towards answering the most fundamental question of: why is there a
universe at all, as opposed to nothingness? In this paper, it is shown that
this seemingly mind-boggling question has a simple logical answer if we accept
that existence in the universe is nothing more than mathematical existence
relative to the axioms of our universe. This premise is not baseless; it is
shown here that there are indeed several independent strong logical arguments
for why we should believe that mathematical existence is the only kind of
existence. Moreover, it is shown that, under this premise, the answers to many
other puzzling questions about our universe come almost immediately. Among
these questions are: why is the universe apparently fine-tuned to be able to
support life? Why are the laws of physics so elegant? Why do we have three
dimensions of space and one of time, with approximate locality and causality at
macroscopic scales? How can the universe be non-local and non-causal at the
quantum scale? How can the laws of quantum mechanics rely on true randomness
Public Key Infrastructure based on Authentication of Media Attestments
Many users would prefer the privacy of end-to-end encryption in their online
communications if it can be done without significant inconvenience. However,
because existing key distribution methods cannot be fully trusted enough for
automatic use, key management has remained a user problem. We propose a
fundamentally new approach to the key distribution problem by empowering
end-users with the capacity to independently verify the authenticity of public
keys using an additional media attestment. This permits client software to
automatically lookup public keys from a keyserver without trusting the
keyserver, because any attempted MITM attacks can be detected by end-users.
Thus, our protocol is designed to enable a new breed of messaging clients with
true end-to-end encryption built in, without the hassle of requiring users to
manually manage the public keys, that is verifiably secure against MITM
attacks, and does not require trusting any third parties
Quantum Fluid Dynamics on the Hypersphere
It is known from quantum mechanics that particles are associated with wave
functions, and that the probability of observing a particle at some future
location is proportional to the squared modulus of the amplitude of its wave
function. Although this statistical relationship is well quantified, the
interpretations have remained controversial, with many split between the
classical Copenhagen interpretation and some variation of the de Broglie-Bohm
pilot wave models. Recent experiments with Hydrodynamic Quantum Analogs (HQAs)
have demonstrated that droplets of real fluid may achieve stable dynamical
states, where interaction of the droplets with their own ripples results in
motion analogous to the motion of particles subject to the guiding equation
under the pilot wave models. Indeed, many effects previously thought to be
exclusively quantum have now been observed as emergent phenomena in these
macroscopic HQAs. This has motivated us to explore the possibility that quantum
mechanics may actually be the result of fluid dynamics on some real quantum
scale fluid. In this paper, we show that if there is a real quantum scale fluid
having dynamics analogous to the fluid in HQAs, then this fluid must be a
superfluid, and the dynamics of that fluid must take place on the surface of a
4-dimensional hypersphere. Under the influence of cosmological inflation, we
further show that these bouncing droplets would have the illusion of a property
analogous to rest mass, and that the principles of inertia, momentum,
mass-energy equivalence, general relativity, the uncertainty principle and the
appearance of a time-like dimension can all be derived for droplets as purely
emergent phenomena from the fluid dynamics of this system. As such, we believe
that this model merits consideration as a potential foundation for a new
unifying theory of physics at all scales
A general reduction method for one-loop N-point integrals
In order to calculate cross sections with a large number of particles/jets in
the final state at next-to-leading order, one has to reduce the occurring
scalar and tensor one-loop integrals to a small set of known integrals. In
massless theories, this reduction procedure is complicated by the presence of
infrared divergences. Working in n=4-2*epsilon dimensions, it will be outlined
how to achieve such a reduction for diagrams with an arbitrary number of
external legs. As a result, any integral with more than four propagators and
generic 4-dimensional external momenta can be reduced to box integrals.Comment: 5 pages Latex, 1 eps figure included, uses npb.sty (included). Talk
presented at the conference: Loops and Legs in Quantum Field Theory, April
2000, Bastei, German
Time-Resolved Visualization of Instability Waves in a Hypersonic Boundary Layer
LAMINAR-TURBULENT transition in hypersonic boundary
layers remains a challenging subject. This is especially true of the hypervelocity regime, in which an intriguing phenomenon is the possible damping of second-mode disturbances by chemical and vibrational nonequilibrium processes. To generate flows with sufficiently high enthalpy to investigate such effects, the use of shock-tunnel facilities is necessary; furthermore, it is now generally accepted that direct measurements of the instability mechanisms active within the boundary layer, together with a characterization of
the freestream disturbance environment, are required, as simple measurements of transition locations can lead to ambiguous conclusions. However, as difficult as the accurate measurement of instability waves in conventional hypersonic facilities can be, in shock tunnels it is appreciably more so. For identical unit Reynolds numbers, the higher stagnation temperature in a shock tunnel means that the dominant second-mode disturbances lie at even higher frequencies (typically hundreds of kHz or higher); moreover, because of the destructive testing environment, hot-wire techniques,
a staple for instability measurements in conventional tunnels, cannot be used. Fast-response pressure transducers are an obvious alternative, but recent experiments have highlighted the challenging nature of interpreting data from mechanically sensitive sensors in the high-noise environment of a shock tunnel, especially without accompanying stability computations. Measurements with recently developed atomic-layer thermopile (ALTP) heat-flux sensors show promise, though their use has yet to be demonstrated in shocktunnel
facilities
Reduction formalism for dimensionally regulated one-loop N-point integrals
We consider one-loop scalar and tensor integrals with an arbitrary number of
external legs relevant for multi-parton processes in massless theories. We
present a procedure to reduce N-point scalar functions with generic
4-dimensional external momenta to box integrals in (4-2\epsilon) dimensions. We
derive a formula valid for arbitrary N and give an explicit expression for N=6.
Further a tensor reduction method for N-point tensor integrals is presented.
We prove that generically higher dimensional integrals contribute only to order
\epsilon for N>=5. The tensor reduction can be solved iteratively such that any
tensor integral is expressible in terms of scalar integrals. Explicit formulas
are given up to N=6.Comment: 21 pages Latex, 1 eps figur
Production and perception of speaker-specific phonetic detail at word boundaries
Experiments show that learning about familiar voices affects speech processing in many tasks. However, most studies focus on isolated phonemes or words and do not explore which phonetic properties are learned about or retained in memory. This work investigated inter-speaker phonetic variation involving word boundaries, and its perceptual consequences. A production experiment found significant variation in the extent to which speakers used a number of acoustic properties to distinguish junctural minimal pairs e.g. 'So he diced them'—'So he'd iced them'. A perception experiment then tested intelligibility in noise of the junctural minimal pairs before and after familiarisation with a particular voice. Subjects who heard the same voice during testing as during the familiarisation period showed significantly more improvement in identification of words and syllable constituents around word boundaries than those who heard different voices. These data support the view that perceptual learning about the particular pronunciations associated with individual speakers helps listeners to identify syllabic structure and the location of word boundaries
- …