# perturbation

## Definitions

• WordNet 3.6
• n perturbation the act of causing disorder
• n perturbation a disposition that is confused or nervous and upset
• n perturbation activity that is a malfunction, intrusion, or interruption "the term `distress' connotes some degree of perturbation and emotional upset","he looked around for the source of the disturbance","there was a disturbance of neural function"
• n perturbation (physics) a secondary influence on a system that causes it to deviate slightly
• n perturbation an unhappy and worried mental state "there was too much anger and disturbance","she didn't realize the upset she caused me"
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Webster's Revised Unabridged Dictionary
• Perturbation (Astron) A disturbance in the regular elliptic or other motion of a heavenly body, produced by some force additional to that which causes its regular motion; as, the perturbations of the planets are caused by their attraction on each other.
• Perturbation The act of perturbing, or the state of being perturbed; esp., agitation of mind.
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Century Dictionary and Cyclopedia
• n perturbation The act of perturbing, or the state of being perturbed; disturbance; disorder; especially, disquiet of mind; restlessness or want of tranquillity of mind; commotion of the passions.
• n perturbation Variation; especially, irregular or violent variation.
• n perturbation A cause of disquiet.
• n perturbation In astronomy, a deviation of the motion of a planet or comet from a fixed orbit or from its regular velocity in that orbit. Perturbations are caused by the gravitating action of bodies other than the primary or central body. They are commonly and conveniently conceived, not as drawing the planets out of their orbits, but as consisting in gradual changes of the elements of the orbits themselves. All perturbations due to gravitation are, strictly speaking, periodical. But some of them, which depend upon the relative situation of the orbits of different planets, go through their changes in such vast intervals of time that they are more conveniently regarded as progressive and not periodic, and are termed secular perturbations; while others, depending for the most part upon the relative situations of the planets in their orbits, go through their changes in comparatively short intervals of time, and can only be represented as periodic, and these are technically called the periodic inequalities.
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Chambers's Twentieth Century Dictionary
• ns Perturbation act of perturbing or state of being perturbed: disquiet of mind: irregular action, esp. (astron.) the disturbance produced in the simple elliptic motion of one heavenly body about another by the action of a third body, or by the non-sphericity of the principal body
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## Etymology

Webster's Revised Unabridged Dictionary
L. perturbatio,: cf. F. perturbation,
Chambers's Twentieth Century Dictionary
Fr.,—L. perturbāre, -ātumper, thoroughly, turbāre, to disturb—turba, a crowd.

## Usage

### In literature:

His very lack of perturbation added weight to the statement.
"The Bat" by Avery Hopwood
Soames' perturbation was so great on that occasion that he feared it must unfailingly be noticed.
"The Yellow Claw" by Sax Rohmer
Moze was lying down, but the others were whining and howling in a state of great perturbation.
"The Last of the Plainsmen" by Zane Grey
When the men did not gamble something immediate and perturbing was on their minds.
"To the Last Man" by Zane Grey
Michael meantime had been travelling down from London without perturbing himself over the scene with his father which he knew lay before him.
"Michael" by E. F. Benson
And at the roots strange poisonous flowers lie writhing in perturbed slumber.
"The Works of Edgar Allan Poe Volume 2 (of 5) of the Raven Edition" by Edgar Allan Poe
The minds of the people are perturbed.
"China and the Manchus" by Herbert A. Giles
After a while he walked off to his wife's room, still perturbed in spirit.
"The Prime Minister" by Anthony Trollope
Mrs. Mumpson sank back in her chair, but her mode of rocking betokened a perturbed spirit.
"He Fell in Love with His Wife" by Edward P. Roe
When she heard this, Grace Carter, the wife of Major Carter, one of the surgeons at the Ancon Hospital, was greatly perturbed.
"The Lost Road" by Richard Harding Davis
Vast periods of time are required for the development of the large consequences of planetary perturbation.
"Great Astronomers" by R. S. Ball
The count was more perturbed than ever by the condition of his affairs, which called for some decisive action.
"War and Peace" by Leo Tolstoy
But the prince's mental perturbation increased every moment.
"Title: The Idiot" by Fyodor Dostoyevsky
But she did not reveal what she thought and he became more perturbed.
"When Egypt Went Broke" by Holman Day
Why should her lover be so perturbed, she wondered?
"The Red Year" by Louis Tracy
His first perturbation had passed and he began actually to enjoy himself.
"Ruth Fielding Homeward Bound" by Alice B. Emerson
Ten o'clock came, when a larger portion of the audience was again perturbed by railway warnings.
"Bygones Worth Remembering, Vol. 2 (of 2)" by George Jacob Holyoake
Mr. Stagg cast a glance upward at the perturbed tom-cat.
"Carolyn of the Corners" by Ruth Belmore Endicott
Thibault found himself agitated with the perturbations of a dawning passion; he accused himself of it as a crime.
"The New-York Weekly Magazine" by Various
The fact, however, that Elma's father had engaged detectives was rather perturbing.
"The Voice from the Void" by William Le Queux
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### In poetry:

Its grasses by the top;
The rains thereon that drop
Perturb
With drip acerb
"To The Dead Cardinal Of Westminster" by Francis Thompson
An agitation of the air,
A perturbation of the light
Would turn on its hinge that night.
"End Of Summer" by Stanley Kunitz
How I am pleased with thee, sweet girl! But do
Shake off this perturbation, be not anxious,
Be not alarmed, I want to hear thee talk -
Be cheerful.
"Nathan The Wise - Act V" by Gotthold Ephraim Lessing
These perturbations, this perpetual jar
Of earthly wants and aspirations high,
Come from the influence of an unseen star,
An undiscovered planet in our sky.
"Haunted Houses. (Birds Of Passage. Flight The First)" by Henry Wadsworth Longfellow
All summer cannot quicken it with heat,
Nor Spring perturb it with a budding bough,
Nor all the glittering devils of the sleet
In snowing Winter rack its quiet now.
"The Golden Corpse" by Stephen Vincent Benet
"To-day my soul clasps Form; but where is my troth
Of yesternight with Tune: can one cleave to both?"
- "Be not perturbed," said she. "Though apart in fame,
As I and my sisters are one, those, too, are the same.
"Rome: The Vatican-Sala Delle Muse." by Thomas Hardy

### In news:

Researchers Provide Systems-Level Dissection of Regulatory Perturbations in Cancer.
A worried-looking Demi Moore looks perturbed in between takes on the set.
Kinases have been the target of extensive research, and there has been significant interest in developing assays that measure the endogenous activities of kinases and their perturbation by small molecules.
At one heated point in Monday night's South Carolina Democratic debate, a perturbed Barack Obama finally blurted out to Hillary Clinton what millions of others have been thinking these past weeks.
And an internationally acknowledged expert on the applied- mathematics technique known as perturbation, died April 17 at Albany Medical Center Hospital.
You know the one — full-sized American steel with a low-profile tow rack in the bed, the claws of which protrude out of the tailgate like a perturbed crab looking to pinch pinch a car.
Perturbations to their structures caused by mysterious rocketing objects.
Those perturbations tip the researchers that a sunspot is forming.
Those perturbations are what tip the researchers that a sunspot is forming.
Our company recently implemented a policy that has quite a few people perturbed, myself included.
I was both pleased and perturbed by the "On the Runway" story in the Sunday New York Times Style section on January 30th.
Preseason or not, there's nothing easier to predict than Rick Carlisle being perturbed after a poor defensive performance.
NBA Playoff primer, plus a pick that might perturb you.
Baseball Stadiums' Peanut -Free Seating Perturbs Some Fans.
Councilmember Daniel Dromm says he is perturbed by the pigeon poop problem casting a shadow over the 74th Street station on Roosevelt Avenue, which hosts the No.
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### In science:

Substituting the above form of the perturbed variables into eqs.(1-3) and combining the resulting velocity ﬁeld and the perturbed continuity equation in the slow mode limit (ω << Ω), we get an implicit relation between the perturbing potential and the perturbed surface density of the disc.
Low frequency m=1 normal mode oscillations of a self-gravitating disc
The expansion up to second order in the linear perturbations of the action (81) is useful to obtain the classical equations of motion for the perturbations and to calculate the spectra of the primordial perturbations generated during inﬂation, as we have seen in the previous section for a single scalar ﬁeld.
Early Universe: inflation and cosmological perturbations
In discussing perturbative predictions for high-energy colliders, it is important to remember that non-perturbative effects can often be as large as higher-orders of perturbation theory.
Moriond 2009, QCD and High Energy Interactions: Theory Summary
The continuous production of perturbations around an inﬂating FLRW background is a decidedly quantum phenomenon: any classical perturbations are diluted away during inﬂation, while perturbations of quantum origin can develop a non-zero super-Hubble amplitude.
Primordial Fluctuations in String Cosmology
The physics that drives the rise in activity is a combination of the non-perturbative total pp cross-section; the non-perturbative physics of beam remnants, diffraction, and multiple partonic scattering; and perturbative low-pT QCD scattering.
THE TOOLS AND MONTE CARLO WORKING GROUP Summary Report from the Les Houches 2009 Workshop on TeV Colliders
The most general possible set of density perturbations is a linear combination of an adiabatic density perturbation and some isocurvature perturbations.
Cosmic Microwave Background Mini-review
Isocurvature means that the set of individual density perturbations adds to zero, for example, matter perturbations compensate radiation perturbations so that the total energy density remains unperturbed, i.e., δρ for matter is −δρ for radiation.
Cosmic Microwave Background Mini-review
The most widely applied methods (in ascending order of effectiveness) include perturbation theory, tadpole-improved (partially resummed) perturbation theory, renormalization group methods, and the non-perturbative evaluation of improvement conditions.
Review of lattice results concerning low energy particle physics
It is well known that the strong variable gravitational ﬁeld of the inﬂationary universe inevitably generates primordial density perturbations (i.e. scalar perturbations) and relic gravitational waves (i.e. tensor perturbations) [4, 5].
Testing inflationary consistency relations by the potential CMB observations
From this assumption alone we cannot conclude that backreaction would be small, because the perturbations of the expansion rate (and the distance) depend on ﬁrst and second derivatives of the metric perturbations, the latter of which become large at the same time as the density perturbations.
Backreaction in late-time cosmology
Estimates in ﬁrst order perturbation theory [4, 6, 52, 85–87] cannot resolve the issue, because the average of the ﬁrst order perturbation vanishes, and the contribution of the square of the ﬁrst order perturbations is not gauge-invariant without the contribution of the intrinsic second order perturbations8 .
Backreaction in late-time cosmology
In the second set of simulations, we include nonstochastic perturbations to the optics due to solid body misalignments, surface perturbations of the ma jor optics elements, and warping and misalignment of the individual sensors in the focal plane (see Table A1 for approximate levels of the ma jor perturbations).
Spurious Shear in Weak Lensing with LSST
In phenomenological studies of DE models, the default assumptions concerning DE perturbations is that (i) pressure perturbations are related to density perturbations through c2 s = 1, and that (ii) anisotropic stress is negligible.
TASI Lectures on Cosmological Perturbations
The gauge invariant metric perturbations are Ψ, the Newtonian potential and Φ, the perturbation to the intrinsic spatial curvature, which are related to the density perturbation through a generalized Poisson equation in §IIC.
Toward Understanding CMB Anisotropies and Their Implications
Before combining the previous non-perturbative results with the perturbative correction to Rτ , let us test the accuracy of the resummed (αsβ1 )n perturbative result of .
QCD tests from $e^+e^- \rar I=1~$ hadrons data and implication on the value of $\alpha_s$ from $\tau$-decays
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