Phys 111 Dr. Echols Lecture Focus Questions
Explain how more electrons will be emitted when the intensity of a light shining on metal increases
"Energy is proportional to "(Ampl)^2" which is proportional to "Intensity"
Explain with a picture and a few words why the speed of light being a constant for all observers regardless of their state of constant velocity motion seems paradoxical?
(picture with the dude on a hoverboard going 1/3C with another dude under him holding a laser beam going the speed of C) C - (1/3)C should equal (2/3)C but it actually just equals C
When string theorists try to calculate the string coupling constant what do they find?
(string coupling constant) x 0 = 0 This means the string coupling constant can literally be anything
How does the force in quantum electrodynamics work?
...
Using today's particle accelerators what length scale can be probed? How does this length compare with the Planck length? Will a manmade particle accelerator ever be able to probe the Planck length?
...
What is the more precise answer for how string theory allows for a consistent theory of quantum gravity
...
Why are there an infinite number of massive expected string particles in integer multiples of the Planck mass>
...
Name three possible scenarios for which string theory could be validated.
1) Discovery of superpartner particles 2) ? 3) ?
Starting with the equivalence principle, explain the logical connections allowing Einstein to discover the general theory of relativity.
1) Equivalence principle 2) Showed that acceleration warps spacetime 3) Seems to imply that gravity is warped spacetime
What are the four known fundamental forces of nature? Give an example of each
1) Gravity ex- an apple falling to the ground 2) Electromagnetic force ex- keeps us from falling through the floor 3) Strong nuclear force ex- Holds quarks together in the nuclues 4) Weak nuclear force ex- Responsible for the decay of atoms and fundamental particles such as uranium, muons
What are two consequences of quantum geometry?
1) Mass in black holes is greater than Planck size 2) Universe began with some size
Name two technological applications of Einstein's famous equation, E=mc2
1) Nuclear power 2) Particle colliders
Name two early confirmations of Einstein's general theory of relativity.
1) Precession of the perihelion of Mercury 2) In 1919, the bending of starlight by a gravitation field (like the sun's) during a total lunar eclipse
What are the goals of string theory? (In class we discussed three related goals)
1) Resolve the conflict between general relativity (GR) and quantum mechanics (QM) 2) Unify all the forces of nature 3) A Theory of Everything
Name three problems with figure 3.5 (the pic of the sun in warped space)
1) Space is shown to bend in only 2 dimensions 2) Doesn't show warping of time 3) There is no external force pulling the sun downwards like a ball on a trampoline
Where in the universe do physicists and astronomers have strong evidence to suggest the existence of black holes? What is the evidence?
1) Stellar remnants in binary star system (x-rays coming from nothing) 2) Masses of black holes can be determined by observing orbiting mass 3) Detecting gravitational waves due to black hole mergers
Name three consequences of large string tension
1) Strings become very small (Planck length) 2) The natural energy scale is the Planck mass 3) You get many different string excitations with mass of integer multiples of the Planck mass
What two ideas (postulates) form the the foundation for Einstein's special theory of relativity?
1) The speed of light in a vacuum is the same regardless of how you move negative to the light 2) The principle of relativity
What is (are) the conflict(s) between general relativity and quantum mechanics?
1) There are an infinite number of infinities 2) The quantum foam is rough
Name three reasons why we might expect supersymmetry to be a supersymmetry of nature?
1) There are other spacetime symmetries that have been found to be obeyed in nature. Why not SUSY? 2) If nature obeys SUSY, then these forces unify at high energy (or short distance) 3) Fine tuning problem - Without SUSY, the equations involving the Higgs boson require "fine tuning". With SUSY, no fine tuning required
In the past when physicists tried to make a quantum field theory of non-point particles what problems did they encounter? Who were some of these physicists?
1) There were tacyons 2) The probabilities didn't work out Feynman, Heisenberg
Name two major difficulties Greene and collaborators encountered when comparing the "after" space-tearing flop transition C-Y manifold with it's mirror
1) Very difficult to find the dual space 2) Calculations in the dual space are very difficult and need lots of computer programming
What are two consequences of quantum geometry?
1) mass in black holes is greater then plank size 2) universe began with some size
What are the two types of vibrational energies associated with a string? Briefly explain what each energy corresponds to?
1) ordinary vibration: vibration energy of string itself 2) uniform vibration: qm energy of motion
Under what conditions do the strong, electromagnetic, and weak forces unify?
1) supersymmety 2) high energy/ short distances
What are the two Heisenberg uncertainty relations we discussed in class?
1) uncertainty in "position" times uncertainty in "momentum" > or equal to h-bar over two, 2) uncertainty in "energy" times uncertainty in "time" > or equal to h-bar over two
How many spatial dimensions are being represented in figures 8.4, 8.7, 8.8, 8.9, and 8.10?
8.10-8, 8.7-4
How do you explain seeing an interference pattern when one photon at a time illuminates a double slit apparatus over a long period of time according to Schrodinger?
According to him, the one photon is a probability wave that has equal probability of going through both slits
What is Louis de Broglie's contribution to physics?
All matter has wavelengths (matter waves)
If low intensity light is shining on a metal and no electrons are emitted, using classical physics what do we expect to happen as the intensity is increased?
As intensity of the light increases, we expect more electrons to be emitted
Witten discovered two paths to M-theory from the previously known five distinct string theories. Explain how an extra dimension emerges for the two paths to M-theory Witten discovered. What is (are) the shape(s) of the extra dimension that emerges?
As the Heterotic-E string coupling constant is increased, the string gets stretched into a ribbon shape. As the Type IIA string coupling constant is increased, the string becomes inner-tube/donut shaped
In light of M-theory developments in what sense are strings still special?
At weak string coupling, the strings are low mass objects.
What is orbifolding?
Attachment of points in one Calabi-Yau to create a new distinct Calabi-Yau space
What is orbifolding?
Attachment of points in one Calabi-Yau using precise mathematical rules to create a new distinct Calabi-Yau space
What is the tool used by physicists to understand the approximate equations of string theory?
BPS states
Why does Stephen Hawking say, Einstein was confused, not the quantum theory?
Because Einstein could not accept the fact quantum physics is based on probability, "God does not play dice with the universe."
Why do some people say the "M" in M-theory refers to membrane?
Because in M-theory, the strings become 2-D membranes (2-branes)
Why can we not see the wavelength of a baseball flying through the air?
Because the larger the mass, the smaller the wavelength. A baseball's , mass is too large
Why can't I measure the position of a particle to high precision with long wavelength light?
Because the low energy photon provides poor resolution
Using a light clock, clearly state the argument for why time slows for moving clocks relative to stationary observers.
Because the photon in the light clock must travel a longer distance in the moving clock compared to the resting one. Since the distance increases, the time it takes for the photon to do a tick also increases
As Slim stands still on the outside edge of the tornado ride moving at constant speed, why is he accelerating?
Because the spinning of the ride is causing him to change directions
Why do string theorists no longer have to worry about the tachyon particle traveling faster than the speed of light?
Because they were able to combine the 5 string theories into one M-theory?
Why can a string not be used to probe sub-planck-length distances?
Because when you increase the energy of a string, it excited to a new, more massive particle
What type of particles did the first string theory explain
Bosons
Name a physicist who worked on orbifolding.
Brian Greene
What needs to happen for a string to have small or zero mass?
Cancellations need to take place (I only got half credit with this answer on the quiz so rip)
Into what particles does a muon decay? What force plays a role in muon decay?
Decay into an electron, a muon neutrino, and an electron anti-neutrino. The weak nuclear force plays a role in muon decay
Is string theory accepted?
Depends on who you ask. String theorists say yes because its going in the right direction. Other say no, its just a theory that hasn't been verified.
What is the physical significance of the string coupling constant?
Dictates how strongly the strings interact
What string theory success led to the 2nd string theory revolution?
Dr. Witten our lord and savior showed that all string theories related to one another (m-theory)
What's the difference between an electron and a photon?
Electron: A matter particle, has mass Proton: A force particle, no mass In string theory, the difference between them is the way they vibrate
What did Planck have to assume to properly predict blackbody radiation?
Energy of quanta is proportional to frequency
How does the string uniform motion energy depend on the radius of the compact space?
Eu.v. = Nu.v./R
How does the string winding energy depend on the radius of the compact space?
Ew = NwR
Define supersymmetry
For every fermion particle there is a superpartner boson; and vise versa
Does string theory say it is impossible to have more than one time dimension?
For simplicity, we're gonna assume theres only one
Why does the string tension need to be so large?
For there to be a quantum theory of gravity (force of gravity. The force of gravity is very weak, so there needs to be large string tension
Name the superpartners of the particles in the standard model and their corresponding spin.
Force particle (boson) - Photon: spin of 1 - Photino: spin of 1/2 Matter particle (Fermion) - Electron: spin of 1/2 - Selectron: spin of 0
As viewed from earth how does the lifetime of an approaching muon compare to a muon at rest? How does this change in a muon's lifetime affect how far the muon travels as viewed from earth?
From earth, the lifetime of the approaching muon is increased due to time dilation. The muon's lifetime at rest is 2x10^-6 but the lifetime of one approaching Earth is 10 times greater. This change means that the muon is able to reach the earth.
What is the equivalence principle? Explain with the aid of a picture.
Gravity is indistinguishable from acceleration. Pic of some dude in an elevator with an apple in deep space vs on Earth.
Has string theory been able to predict the mass of a graviton? An electron?
Has predicted the mass of a graviton is 0 Cannot predict mass of an electron :(
What point does Greene make by introducing the word syzygy?
He makes the point that BPS states are supersymmetric, have minimal mass for a given charge, and are highly constrained
What is Einstein's biggest blunder?
He put a term in his equations to suggest that the universe is static, when in fact it is expanding.
What was Witten's insight into the space-tearing flop transition?
He showed that the virtual string world sheet protects the tearing space from catastrophic consequences
When R is large, what are the heavy probes and light probes? Why?
Heavy - winding light - uniform
When R is small, what are the light probes and heavy probes? Why?
Heavy- uniform Light - winding
In what sense did Newton unify the heavens and earth with his theory of gravity?
His law showed that the force causing an apple to fall from a tree is the same one holding the moon in orbit
When Kaluza first postulated extra spatial dimensions in 1919 what was his motivation? How were his ideas received by Einstein? Why was his theory not accepted?
His motivation was to unify the electromagnetic force with gravity. Einstein liked it and then he didn't. It made an incorrect prediction about the charge to mass ratio of an electron
How does Einstein's general theory of relativity resolve the conflict between Newton's theory of gravity and Einstein's theory of special relativity?
His theory gives us a way to visualize gravity. We now know through GR that gravity is the same speed as light, not faster than it.
Using the tornado ride as an example, explain how space is warped (or curved)
In the tornado ride, Slim's ruler is contracted through the Lorentz contraction, so he measures a greater circumference that in he was off the ride. On the ride: C > 2(pi)r
How does string theory force us to think differently about space?
It forces us to recognize extra dimensions of space that we cannot see
What is the biggest conflict in modern day physics that string theory hopes to resolve? What problems in physics require resolution of this conflict in order to be more understood?
It hopes to resolve the problem of quantum gravity, the fact that QM and gravity don't work together
Explain how it is possible to understand the idea that two people moving away from each other will view the other person's clock as moving slower than theirs
It is possible to understand this based on the principle of time dilation
What makes a black hole black?
Light cannot escape a black hole's gravitational field once it passes the event horizon
What is a light clock?
Made of two mirrors with a photon that bounces between them. 1 tick = 1 nanosecond
Explain in one concise sentence the essence of Einstein's general theory of relativity.
Matter warps space and time and matter moves in that warped spacetime.
What is the reductionist viewpoint?
Means that you can know everything (even things like love and emotion) with equations and physics
What is mirror symmetry in string theory? Why is it important to mathematicians and string theorists? Give an example
Mirror symmetry means the physics is the same for an orbifolded Calabi-Yau from 3 holes in even dimensions to 3 holes in odd dimensions. This is useful because calculations in one C-Y space may be difficult the same calculations in the dual space is easy. ex) Math problem = "spheres in a C-Y space
To conclude that the minimum size for a dimension is grater that 1 (the Planck size), what type of probe must be used? Why is this the natural choice of probe?
Must use the low mass probe because it is available to us
What is the conflict between Newton's theory of gravity and Einstein's theory of special relativity?
Newton;s theory says that gravity acts instantaneously across space but Einstein says that nothing can go faster than the speed of light
Can space tear in Einstein's general theory of relativity? Explain.
No
If supersymmetry is discovered at the Large Hadron Collider, will string theory be validated? Explain.
No because supersymmetry is in point particle theories too
If supersymmetry is not discovered at the Large Hadron Collider, will string theory be proven wrong? Explain.
No because the the superpartner particles might not be measurable with current tech
Explain how a fundamental string can have mass
No cancellations can take place. You also need to increase the energy
Is the geometry you learned in high school obeyed on the tornado ride? Explain.
No. The geometry we learned in high school is based on flat, static space. The space on the ride is warped
What physical properties stay the same and which ones change in a space-tearing flop transition?
Particle types stay the same. Mass of the particles change slowly and continuously
Explain using the equivalence principle and a picture why light bends in a gravitational field
Pic of two dudes in a box shooting a laser. One guy is near a black hole. The other is accelerating. Their laser beams are curving the same way tho Light bends near a black hole due to large gravitational field but since a=g, it also bends due to large acceleration
Can large spatial dimensions tear? Explain why we believe this to be true or not.
Probably yes, because space is space, but we don't know for sure
Explain how you can understand the four big concepts in quantum mechanics using the double slit experiment
Quanta-? Duality-? Probabilistic-? Uncertainty-? lol help
Consider a string in a Universe with a compact circular dimension ten times the Planck length (i.e. R=10 in Planck length units). If the winding number is 3 and the uniform vibration number is 2, what is the total energy (in Planck units) from these excitations?
R=10 Nw=3 Nuv=2 Ew=Nw*R Ew=3*10 Ew=30 Euv=Nuv/R Euv=2/10 Euv=.2 Ew+Euv= 30+.2= 30.2
Give an example demonstrating the relativity of simultaneity.
Relativity of simultaneity: Events that are simultaneous to one observer are no longer simultaneous to an observer moving relative to the first Can use the UN train example, Einsteins lightning example, or muon decay
In class we discussed three ways of understanding the relative nature of simultaneity. Choose the one way you like best and explain what is meant by relativity of simultaneity.
Relativity of simultaneity: Events that are simultaneous to one observer are no longer simultaneous to an observer moving relative to the first Can use the UN train example, Einsteins lightning example, or muon decay
What is the difference between Riemannian geometry and Quantum geometry? For our universe, at what length scales is each geometry important?
Riemannian-gr, points, smooth space quantum-plank length, strings, quantum foam
Brian Greene discusses two answers for how string theory resolves the conflict between general relativity and quantum mechanics. Explain the rough answer and why we shouldn't be satisfied with this answer.
Since we can't probe sub-Planck length with strings, the quantum foam isn't a problem anymore. This doesn't mechanically describe anything (what the fock is this answer)
Using the tornado ride as an example, explain how acceleration leads to warping of time.
Slim is on the edge so his acceleration the fastest. By special relativity, his clock has the largest time dilation compared to someone closer to the center, like Jim
Why do we use a light clock instead of a Rolex watch when we discuss how time slows for moving clocks relative to stationary observers?
So that we can visualize the effect better
In what sense did supersymmetry find its beginning in string theory?
String theory, which began with bosons, was able to pair bosons with fermions
Explain the types of dualities depicted in figure 12.10 and give an example of each type.
Strong/weak coupling duality: Type I <-> Heterotic-O R and 1/R / winding and uniform vibration number duality: Heterotic-O <-> Heterotic-E
What is supergravity and how is it related to M-theory?
Supergravity is an 11-D spacetime quantum field theory of gravity. M-theory at low energy is dual to supergravity
What does the super in superstring theory refer to?
Supersymmetry
Make a cartoon sketch showing the before, during and after of a space-tearing flop transition. Why can string theorists not compare physics with the before picture directly with the after picture?
That one pic of the blob splitting and becoming a cute little bow tie The calculations are too difficult
Explain with a picture why the electromagnetic force gets stronger when probed at small distance or high energy?
That one pic with the rotating anti-particle pairs surrounding the electron. At short distances (point A), there is less shielding of the electric charge by the quantum foam than at point B
State three observations about space and time that can be made by observers moving relative to each other.
The consequences of special relativity: 1) Time dilation 2) Lorentz contraction 3) Relativity of simultaneity
How do you explain seeing an interference pattern when one photon at a time illuminates a double slit apparatus over a long period of time according to Feynman?
The electron/photon takes all possible paths simultaneously
In the video we saw, what example was used to depict the conflict between Newton's theory of gravity and Einstein's theory of special relativity?
The example used was the sun suddenly disappearing from our solar system
Newton was embarrassed by what aspect of his theory of gravity?
The fact that he didn't know how gravity worked
What happens to the velocity (or momentum) of a particle when you use short wavelength light to detect its position?
The high energy photon disrupts the momentum of the particle, which means you can determine the potion with high precision but not the momentum
What is meant by the principle of relativity?
The laws of physics don't depend on the experimenters state of constant velocity motion
Does the number of particle families depend on the number of even-dimensional holes or odd-dimensional holes? Explain
The number of particle families does depend on the number of holes because the holes determine how string excitations arrange themselves
For a universe of size R to be dual to a universe of size 1/R, what must happen to the winding mode number and the uniform vibration number?
The numbers must be interchanged
From whose perspective can one easily explain the twin paradox? Explain.
The person at rest because they can observe the clock of the other person moving slower
Make a cartoon sketch showing the before, during and after of a space-tearing flop transition using the mirror Calabi-Yau. Does anything dramatic happen to the mirror Calabi-Yau space during the tear?
The pic of the blob with an oval in it that becomes hourglass-shaped and then an oval again. Nothing catastrophic happens
What happens when you repeat the double slit experiment using electrons instead of photons?
The same results apply
What point is Brian Greene trying to make by introducing the art competition between Slim and Jim? Explain.
The smaller your particle is, the higher resolution you get while probing. Particles can't be bigger than the thing being examined.
What property of a particle determines if its a boson or fermion? Give examples of both types of particles
The spin boson = force particles fermion = matter particles
How is the spin of a particle determined?
The spin creates a magnetic field that the experimentalist can measure using another magnetic field
What space(s) with compact dimension(s) and large extended dimension(s) can we properly visualize with a drawing?
The two dimensional space, (1 large, 1 compact) is the only case we can visulaize
What precedence is there in physics for unification of forces?
The unification of electricity an magnetism by Maxwell
When comparing an R = 10 universe with an R = 1/10 universe, what difficulties arise when a direct measurement of the radius is made?
There are two ways to measure (uniform vibration and winding probe) and they give different measurements
Given the crazy ideas coming from quantum mechanics why should we believe it?
There has never been an experiment that contradicts it
In what sense is quantum chromodynamics (QCD) like QED?
They are both a type of QFT, both have force particles
In what sense are BPS states non-perturbative?
They are non-pertubative because their values transcend the perturbative approximation scheme
In string theory what ARE fundamental particles such as electrons and photons?
They are strings, not points
In particle physics experiments how are the probes of small wavelength created?
They increase the point particle energy
How will two people (such as Gracie and George in the text) moving away from each view time passing on the other person's clock?
They would both view the other person's clock as moving slower than theirs
With the aid of a picture explain what Einstein means by our motion through spacetime is at the speed of light. Locate points of no motion through space and time, and maximal motion through space and time on the diagram.
This is that one graph with a curve representing everything that exists. The y-axis is labelled "Motion through time" and the x-axis is "Motion through space". Our motion is at the point where the curve hits the y-axis ("no motion through space, max motion through time"), meaning that we are traveling through time at the speed of light. The motion of light is at the point where the curve hits the x-axis (no motion through time, max motion through space).
For weak gravitational fields like the earth, does spatial curvature or time curvature have more of an effect?
Time curvature has a greater effect/easier to see on Earth
How does the flow of time on earth compare to an identical clock 6,000 miles above the surface? How do we know?
Time is slower on the on earth compared to the clock above the surface. This is because there is less gravity above the earth than at the surface
From the point of view of the muon at rest, how do we explain the fact that the earth reaches the muon before it decays?
To the muon at rest, the Earth is able to reach it because the space between the Earth and the muon is contracted due to the properties of the Lorentz contraction.
What is the twin paradox?
Two identical twins, one stays on earth, one travels. Traveling twin ages slower
What are the names of the five different consistent superstring theories? In light of the second superstring revolution is five potential theories of everything a problem?
Type I, Type IIA, Type IIB, Heterotic-O, Heterotic-E
Describe how acceleration warps space using only arguments from special relativity
Using the tornado ride example, Jim measures the radius but his ruler is not Lorentz contracted but Slim's is because it is pointing in the direction of motion. Because of this, Slim measures a larger circumference than if he was off the ride
Do we expect to be able to find superpartner particles experimentally? If so, when and where might they be discovered?
We do expect to find them. They may be found at the new International Linear Collider
How can we know that conclusions we reach about a light clocks also apply to a Rolex watch?
We know the tick of the photon and the Rolex watch are synced. For the person wearing the Rolex, they think they are at rest (principle of relativity)
What do we mean by an even or odd-dimensional hole?
We mean a hole ripped within an even or odd-dimensional hole lmao
What do we mean by duality in string theory? Give an example
When physics are identical under different condition ex) when winding and uniform vibration numbers are interchanged and R=1/R
Give an example of the precision of QED
When you compare the theory with its experiments, the agreement better than 1 part in a trillion - That means if you were a billionaire, you would know about every single penny
Can two observers in relative motion agree on the interaction point for two point particles? Explain.
Yes because they only interact at single points
Has something similar to the twin paradox been confirmed experimentally? Explain.
Yes. They have used two jets and atomic clocks to confirm
What was Einstein's happy thought and why did it make him happy?
You can't feel your own weight when you fall. Made him happy because comparing gravity to acceleration makes gravity more understandable
Using a light clock, explain why we can only easily see time slowing for moving clocks relative to stationary observers when the clock moves close to the speed of light.
You have to be moving close to the speed of light to observe the time dilation effects, otherwise the clock would be too slow and the tick would not move any distance
In 1974 what did Schwarz and collaborators show the massless messenger particle of string theory could describe?
a graviton
What do we mean by an even or odd-dimensional hole?
a hole created in either even (2d) or odd (3d) dimensions
If I wanted to detect something with a size of 1cm what wavelength of light would I need to use? Explain.
a wavelength less than 1 cm, high resolution requires small wavelength
Which of the force particles in nature depend on the shape of the compact dimensions and which don't?
all except graviton
Name four characteristics of a wave
amplitude, wavelength, frequency, period
What pattern do you observe on the detection screen when a high intensity light source illuminates a double slit apparatus?
an interference pattern
What pattern do you observe on the detection screen when one photon at a time illuminates a double slit apparatus over a long period of time?
an interference pattern
What string theory success led to the 1st string theory revolution?
anomalies are not anomalies and all fundamental forces can be unified
What is blackbody radiation?
anything with temperature that radiates electromagnetic radiation
How are wavelength and frequency related for light waves?
as frequency increases, wavelength decreases
Where are the extra dimensions we don't see?
at every point in space
What parameters in the standard model might string theory be able to explain?
converts all parameters to string tension (mass, charge, strength)
Who was the first person to properly explain the photoelectric effect?
einstein
Why does string theory need extra dimensions to work?
for probabilities to be in an acceptable range (0-1)
Name some of the particles in the standard model of particle physics. In the quantum field theories describing the standard model, what is the structure of these fundamental particles?
force (gluon, photon, boson, graviton) and matter particles (like electron, muon, tau, etc.) they are point particles
Einstein spent his life trying to unify which forces of nature?
gravity and electromagnetism
Why is the Heisenberg uncertainty relation not relevant for our everyday world?
h-bar is much to small to apply to the macroscopic world, the measurements needed would be impossible to measure
When R is small what are the light probes and heavy probes? Why?
heavy-uniform, light-winding
When R is large what are the heavy probes and light probes? Why?
heavy-winding, light- uniform
If the tornado ride were in deep space far from gravitating objects, in what sense would the ride mimic gravity experienced on earth?
idk something about how the acceleration caused by the spinning pushes the people to sides, as if there was gravity
Explain in words the key features of a quantum field theory
involves quantum mechanics, special relativity, and force fields
Does the number of particle families depend on the number of even-dimensional holes or odd-dimensional holes? Explain.
it does depend on the holes because the number of holes determines how the string excitations arrange themselves
In what sense does string theory simplify our view of fundamental particles?
it makes everything a string which smooths the quantum foam
What is the standard model for particle physics?
made up of strong, weak, and electromagnetic forces (NOT gravity!)
Name a physicist who worked on orbifolding.
my BAD BITCH brian greene
How many space and time dimensions are in the original string theory?
nine space, one time
In the quantum mechanical explanation of blackbody radiation why can't very high-energy photons contribute to the radiated energy?
not enough thermal energy to excite high energy quanta
If the string coupling constant is small (less than 1), how many dimensions does string theory or M-theory have?
only 10 dimensions
In the analogy between blackbody radiation and the warehouse landlord, what physics concepts correspond to people, coins, temperature, furnace setting payment, and money?
oscilators, quanta, temp, energy radiated, energy
According to James Clerk Maxwell, what is light?
oscillating electric and magnetic fields
What happens to spacetime at small space and time scales? How small is small?
particles are created and destroyed in what is called quantum foam. small means plank length
Explain quantum tunneling.
passing through an energy barrier by borrowing energy
What size is a string particle expected to be?
planck length (10^-33 cm)
What is the natural mass scale for a string
planck mass
What is the anti-particle of an electron called?
positron
Name four primary characteristics of quantum mechanics
quanta, duality, probability, uncertainty
What is the quantum electroweak theory, why is it important?
quantum field theory for the electromagnetic and weak force, important because it combines them
Explain how two observers in relative motion can not agree on the interaction point of two strings
relativity of simultaneity
What is the photoelectric effect?
shoot etm light at metal, if frequency of light is high enough electrons emerge from metal
What are the known symmetries of space, time, and motion?
short distance or high energy
If the original string theory is correct (disregard M-theory for the moment), how many spatial compact dimensions are there? What shapes meet the stringent requirements of string theory?
six compact, calabi-yau
In the quantum cafe, why are the ice cubes rattling around in the glasses?
something about how makes it so that you can better know the location of the ice cube, but the ice cube doesn't want its position known. idk but I know that as the cup gets smaller, the ice cube rattles more vigorously
In regards to a compact dimension, how is string motion different from a point-particle?
strings can wind around dimensions and move through dimensions
What is the structure of the fundamental particles in string theory? How does string theory account for the differences between fundamental particle properties like the mass and charge of electrons and quarks?
strings, there is one fundamental particle (the string) and the vibrations give rise to mass and charges
If you wanted to create a wormhole to travel between your house and Cal Poly what would you need to do to space?
tear it
How many space and time dimensions are in M-theory?
ten space, one time
What do you have to assume to properly explain the photoelectric effect?
that QM is correct and that light comes in packets called photons
How are B.P.S. states used to show the strong coupling limit of one string theory is dual to the weak coupling limit of another?
the BPS states are the same at both strong and weak coupling
Being as precise as possible, according to string theory what determines properties of particles we see in our large extended dimensions? You may use the electron mass as an example
the compact dimensions because they determine how a string vibrates, which in turn determines the properties of particles
For a universe of size R to be dual to a universe of size 1/R, what must happen to the winding mode number and uniform vibration number?
the numbers must be interchanged
What is mirror symmetry in string theory? Why is it important to mathematicians and string theorists? Give an example.
the physics is the same for an orbifolded calabi-yau from three holes in even dimensions to three holes in odd dimensions, because calculations in one c-y space may be difficult but the same calculations in the dual space may be easy, math problems ~ "spheres" in a c-y space
When string theory was first discovered what was it used to explain?
the strong force
When comparing an R=10 universe with an R=1/10 universe, what difficulties arise when a direct measurement of the radius is made?
there are two ways to measure (uniform vibration probe and winding probe) and they give different measures
Why can physicists not make precise calculations about the shape of compact dimensions?
they cant because its also in point particle theories
For what values of the string coupling constant does perturbation theory work?
values less than 1
Name some of the interesting phenomena found in the quantum café or h-bar
walk through wall, ice cubes rattling, cigar goes behind Georges head
In string theory what controls the number dimensions which are large and extended instead of being small and compact?
we don't know why
What do we mean by duality in string theory? Give an example.
when physics are identical under different conditions
Are infinities encountered in Q.E.D.? Are they controllable? Why?
yes, they're encountered and controllable because they only have a small finite number
What happens when you try to explain blackbody radiation with classical physics?
you get infinite amount of wavelengths, which implies infinite energy
What happens when calculations are made in a quantum field theory of gravity?
you get uncontrollable infinities
To conclude that the minimum size for a dimension is greater than 1 (the Planck size), what type of probe must be used? Why is this the natural choice of probe?
you must use a low mass probe, because its available to us
