arXiv subjects

Pierre Sikivie

Publications and source records attributed to Pierre Sikivie.

49 records · Page 3Linked to original sources

arXiv1999

Evidence for universal structure in galactic halos

The late infall of dark matter onto a galaxy produces structure (such as caustics) in the distribution of dark matter in the halo. We argue that such structure is likely to occur generically on length scales proportional to $l \sim t_0 v_{rot}$, where $t_0$ is the age of the universe and $v_{rot}$ is the rotation velocity of the galaxy. A set of 32 extended galactic rotation curves is analyzed. For each curve, the radial coordinate is rescaled according to $r\to \tilde r \equiv r (v_0 / v_{rot})$, where we choose $v_0 = 220 km/s$. A linear fit to each rescaled rotation curve is subtracted, and the residuals are binned and averaged. The sample shows significant features near $\tilde r = 40 kpc$ and $\tilde r = 20 kpc$. This is consistent with the predictions of the self-similar caustic ring model of galactic halos.

astro-ph↗

arXiv1998

Caustic rings of dark matter

It is shown that the infall of collisionless dark matter onto isolated galaxies produces a series of caustic rings in the halo dark matter distribution. The properties of these caustics are investigated. The density profile of the caustic is derived for a specific case. Bumps in the rotation curve of NGC 3198 are interpreted as due to caustic rings of dark matter.

astro-ph↗

arXiv1997

Dark matter axions and caustic rings

Contents: 1. The strong CP problem 2. Dark matter axions 3. The cavity detector of galactic halo axions 4. Caustic rings in the density distribution of cold dark matter halos

hep-ph↗

arXiv1996

Dark matter axions '96

Contents: 1. The strong CP problem 2. Dark matter axions 3. The cavity detector of galactic halo axions 4. The phase space structure of cold dark matter halos

hep-ph↗

arXiv1996

What is the spectrum of cold dark matter particles on Earth?

It is argued that the spectrum of cold dark matter particles on Earth has peaks in velocity space associated with particles falling onto the Galaxy for the first time and with particles which have fallen in and out of the Galaxy only a small number of times in the past. Estimates are given for the sizes and velocity magnitudes of the first few peaks. The estimates are based upon the secondary infall model of halo formation which has been generalized to include the effect of angular momentum.

astro-ph↗

arXiv1995

The Pooltable Analogy to Axion Physics

An imaginary character named TSP finds himself in a playroom whose floor is tilted to one side. However, the pooltable in the playroom is horizontal. TSP wonders how this can be. In doing so, he embarks upon an intellectual journey which parallels that which has been travelled during the past two decades by physicists interested in the Strong $CP$ Problem and axion physics.

hep-ph↗

arXiv1995

Sources and Distributions of Dark Matter

In the first section, I will try to convey a sense of the variety of observational inputs that tell us about the existence and the spatial distribution of dark matter in the universe. In the second section, I will briefly review the four main dark matter candidates, taking note of each candidate's status in the world of particle physics, its production in the early universe, its effect upon large scale structure formation and the means by which it may be detected. Section 3 concerns the energy spectrum of (cold) dark matter particles on earth as may be observed some day in a direct detection experiment. It is a brief account of work done in collaboration with J. Ipser and, more recently, with I. Tkachev and Y. Wang.

hep-ph↗

arXiv1994

Casimir Forces between Beads on Strings and Membranes

We develop a general formalism to calculate the force between beads attached to a flat $d$-dimensional membrane due to the quantum fluctuations of the membrane. The interaction potential is derived as a function of $d$ and the membrane energy density, tension, stiffness and temperature. We find that the induced interactions turn off when $d$ exceeds a certain critical dimension. The potential is attractive in all cases where it is non-zero and at finite temperature falls off exponentially for large distances.

hep-th↗

arXiv1994

Stretching Wiggly Strings

How does the amplitude of a wiggle on a string change when the string is stretched? We answer this question for both longitudinal and transverse wiggles and for arbitrary equation of state, {\it i.e.}, for arbitrary relation between the tension $τ$ and the energy per unit length $ε$ of the string. This completes our derivation of the renormalization of string parameters which results from averaging out small scale wiggles on a string. The program is presented here in its entirety.

hep-ph↗

arXiv1993

Axion detection in the milli-eV mass range

We propose an experimental scheme to search for galactic halo axions with mass $m_a \sim 10^{-3}$eV, which is above the range accessible with cavity techniques. The detector consists of a large number of parallel superconducting wires embedded in a material transparent to microwave radiation. The wires carry a current configuration which produces a static, inhomogeneous magnetic field $\vec{B}_0(\vec{x})$ within the detector volume. Axions which enter this volume may convert to photons. We discuss the feasibility of the detector and its sensitivity.

hep-ph↗

arXiv1993

Casimir forces between beads on strings

We consider a string with uniform energy density and tension and with a number of pointlike masses attached at fixed interdistances. We evaluate the effective interaction forces between these masses induced by the quantum fluctuations of the string. For interdistances large compared to the thickness of the string and small compared to the total length, these forces are universal and attractive and fall off, for large distances as $1/r^3$ and for small distances as $1/r$. The attractive nature of these forces creates an instability under which masses added to the string tend to aggregate.

hep-ph↗

arXiv1992

Long Range Forces from Two Neutrino Exchange Revisited

The exchange of two massless neutrinos gives rise to a long range force which couples to weakly charged matter. As has been noted previously in the literature, the potential for this force is $\VN \propto G_{F}^2 / r^5$ with monopole-monople, spin-spin and more complicated interactions. Unfortunately, this is far too small to be observed in present day experiments. We calculate $\VN$ explicitly in the electroweak theory, and show that under very general assumptions forces arising from the exchange of two massless fermions can at best yield $1 / r^5$ potentials.

hep-ph↗

arXiv1992

Wiggly Relativistic Strings

We derive the equations of motion for general strings, i.e. strings with arbitrary relation between tension $τ$ and energy per unit length $ε$. The renormalization of $τ$ and $ε$ that results from averaging out small scale wiggles on the string is obtained in the general case to lowest order in the amount of wiggliness. For Nambu-Goto strings we find deviations from the equation of state $ετ= {\rm constant}$ in higher orders. Finally we argue that wiggliness may radically modify the gauge cosmic string scenario.

hep-ph↗